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diff --git a/doc/refman/RefMan-tac.tex b/doc/refman/RefMan-tac.tex deleted file mode 100644 index 14d95ab8..00000000 --- a/doc/refman/RefMan-tac.tex +++ /dev/null @@ -1,4341 +0,0 @@ -% TODO: unify the use of \form and \type to mean a type -% or use \form specifically for a type of type Prop -\chapter{Tactics -\index{Tactics} -\label{Tactics}} - -A deduction rule is a link between some (unique) formula, that we call -the {\em conclusion} and (several) formulas that we call the {\em -premises}. Indeed, a deduction rule can be read in two ways. The first -one has the shape: {\it ``if I know this and this then I can deduce -this''}. For instance, if I have a proof of $A$ and a proof of $B$ -then I have a proof of $A \land B$. This is forward reasoning from -premises to conclusion. The other way says: {\it ``to prove this I -have to prove this and this''}. For instance, to prove $A \land B$, I -have to prove $A$ and I have to prove $B$. This is backward reasoning -which proceeds from conclusion to premises. We say that the conclusion -is {\em the goal}\index{goal} to prove and premises are {\em the -subgoals}\index{subgoal}. The tactics implement {\em backward -reasoning}. When applied to a goal, a tactic replaces this goal with -the subgoals it generates. We say that a tactic reduces a goal to its -subgoal(s). - -Each (sub)goal is denoted with a number. The current goal is numbered -1. By default, a tactic is applied to the current goal, but one can -address a particular goal in the list by writing {\sl n:\tac} which -means {\it ``apply tactic {\tac} to goal number {\sl n}''}. -We can show the list of subgoals by typing {\tt Show} (see -Section~\ref{Show}). - -Since not every rule applies to a given statement, every tactic cannot be -used to reduce any goal. In other words, before applying a tactic to a -given goal, the system checks that some {\em preconditions} are -satisfied. If it is not the case, the tactic raises an error message. - -Tactics are build from atomic tactics and tactic expressions (which -extends the folklore notion of tactical) to combine those atomic -tactics. This chapter is devoted to atomic tactics. The tactic -language will be described in Chapter~\ref{TacticLanguage}. - -There are, at least, three levels of atomic tactics. The simplest one -implements basic rules of the logical framework. The second level is -the one of {\em derived rules} which are built by combination of other -tactics. The third one implements heuristics or decision procedures to -build a complete proof of a goal. - -\section{Invocation of tactics -\label{tactic-syntax} -\index{tactic@{\tac}}} - -A tactic is applied as an ordinary command. If the tactic does not -address the first subgoal, the command may be preceded by the wished -subgoal number as shown below: - -\begin{tabular}{lcl} -{\commandtac} & ::= & {\num} {\tt :} {\tac} {\tt .}\\ - & $|$ & {\tac} {\tt .} -\end{tabular} - -\section{Explicit proof as a term} - -\subsection{\tt exact \term -\tacindex{exact} -\label{exact}} - -This tactic applies to any goal. It gives directly the exact proof -term of the goal. Let {\T} be our goal, let {\tt p} be a term of type -{\tt U} then {\tt exact p} succeeds iff {\tt T} and {\tt U} are -convertible (see Section~\ref{conv-rules}). - -\begin{ErrMsgs} -\item \errindex{Not an exact proof} -\end{ErrMsgs} - -\begin{Variants} - \item \texttt{eexact \term}\tacindex{eexact} - - This tactic behaves like \texttt{exact} but is able to handle terms with meta-variables. - -\end{Variants} - - -\subsection{\tt refine \term -\tacindex{refine} -\label{refine} -\index{?@{\texttt{?}}}} - -This tactic allows to give an exact proof but still with some -holes. The holes are noted ``\texttt{\_}''. - -\begin{ErrMsgs} -\item \errindex{invalid argument}: - the tactic \texttt{refine} doesn't know what to do - with the term you gave. -\item \texttt{Refine passed ill-formed term}: the term you gave is not - a valid proof (not easy to debug in general). - This message may also occur in higher-level tactics, which call - \texttt{refine} internally. -\item \errindex{Cannot infer a term for this placeholder} - there is a hole in the term you gave - which type cannot be inferred. Put a cast around it. -\end{ErrMsgs} - -An example of use is given in Section~\ref{refine-example}. - -\section{Basics -\index{Typing rules}} - -Tactics presented in this section implement the basic typing rules of -{\CIC} given in Chapter~\ref{Cic}. - -\subsection{{\tt assumption} -\tacindex{assumption}} - -This tactic applies to any goal. It implements the -``Var''\index{Typing rules!Var} rule given in -Section~\ref{Typed-terms}. It looks in the local context for an -hypothesis which type is equal to the goal. If it is the case, the -subgoal is proved. Otherwise, it fails. - -\begin{ErrMsgs} -\item \errindex{No such assumption} -\end{ErrMsgs} - -\begin{Variants} -\tacindex{eassumption} - \item \texttt{eassumption} - - This tactic behaves like \texttt{assumption} but is able to handle - goals with meta-variables. - -\end{Variants} - - -\subsection{\tt clear {\ident} -\tacindex{clear} -\label{clear}} - -This tactic erases the hypothesis named {\ident} in the local context -of the current goal. Then {\ident} is no more displayed and no more -usable in the proof development. - -\begin{Variants} - -\item {\tt clear {\ident$_1$} {\ldots} {\ident$_n$}} - - This is equivalent to {\tt clear {\ident$_1$}. {\ldots} clear - {\ident$_n$}.} - -\item {\tt clearbody {\ident}}\tacindex{clearbody} - - This tactic expects {\ident} to be a local definition then clears - its body. Otherwise said, this tactic turns a definition into an - assumption. - -\item \texttt{clear - {\ident$_1$} {\ldots} {\ident$_n$}} - - This tactic clears all hypotheses except the ones depending in - the hypotheses named {\ident$_1$} {\ldots} {\ident$_n$} and in the - goal. - -\item \texttt{clear} - - This tactic clears all hypotheses except the ones depending in - goal. - -\item {\tt clear dependent \ident \tacindex{clear dependent}} - - This clears the hypothesis \ident\ and all hypotheses - which depend on it. - -\end{Variants} - -\begin{ErrMsgs} -\item \errindex{{\ident} not found} -\item \errindexbis{{\ident} is used in the conclusion}{is used in the - conclusion} -\item \errindexbis{{\ident} is used in the hypothesis {\ident'}}{is - used in the hypothesis} -\end{ErrMsgs} - -\subsection{\tt move {\ident$_1$} after {\ident$_2$} -\tacindex{move} -\label{move}} - -This moves the hypothesis named {\ident$_1$} in the local context -after the hypothesis named {\ident$_2$}. - -If {\ident$_1$} comes before {\ident$_2$} in the order of dependences, -then all hypotheses between {\ident$_1$} and {\ident$_2$} which -(possibly indirectly) depend on {\ident$_1$} are moved also. - -If {\ident$_1$} comes after {\ident$_2$} in the order of dependences, -then all hypotheses between {\ident$_1$} and {\ident$_2$} which -(possibly indirectly) occur in {\ident$_1$} are moved also. - -\begin{Variants} - -\item {\tt move {\ident$_1$} before {\ident$_2$}} - -This moves {\ident$_1$} towards and just before the hypothesis named {\ident$_2$}. - -\item {\tt move {\ident} at top} - -This moves {\ident} at the top of the local context (at the beginning of the context). - -\item {\tt move {\ident} at bottom} - -This moves {\ident} at the bottom of the local context (at the end of the context). - -\end{Variants} - -\begin{ErrMsgs} - -\item \errindex{{\ident$_i$} not found} - -\item \errindex{Cannot move {\ident$_1$} after {\ident$_2$}: - it occurs in {\ident$_2$}} - -\item \errindex{Cannot move {\ident$_1$} after {\ident$_2$}: - it depends on {\ident$_2$}} - -\end{ErrMsgs} - -\subsection{\tt rename {\ident$_1$} into {\ident$_2$} -\tacindex{rename}} - -This renames hypothesis {\ident$_1$} into {\ident$_2$} in the current -context\footnote{but it does not rename the hypothesis in the - proof-term...} - -\begin{Variants} - -\item {\tt rename {\ident$_1$} into {\ident$_2$}, \ldots, - {\ident$_{2k-1}$} into {\ident$_{2k}$}} - - Is equivalent to the sequence of the corresponding atomic {\tt rename}. - -\end{Variants} - -\begin{ErrMsgs} - -\item \errindex{{\ident$_1$} not found} - -\item \errindexbis{{\ident$_2$} is already used}{is already used} - -\end{ErrMsgs} - -\subsection{\tt intro -\tacindex{intro} -\label{intro}} - -This tactic applies to a goal which is either a product or starts with -a let binder. If the goal is a product, the tactic implements the -``Lam''\index{Typing rules!Lam} rule given in -Section~\ref{Typed-terms}\footnote{Actually, only the second subgoal will be -generated since the other one can be automatically checked.}. If the -goal starts with a let binder then the tactic implements a mix of the -``Let''\index{Typing rules!Let} and ``Conv''\index{Typing rules!Conv}. - -If the current goal is a dependent product {\tt forall $x$:$T$, $U$} (resp {\tt -let $x$:=$t$ in $U$}) then {\tt intro} puts {\tt $x$:$T$} (resp {\tt $x$:=$t$}) - in the local context. -% Obsolete (quantified names already avoid hypotheses names): -% Otherwise, it puts -% {\tt x}{\it n}{\tt :T} where {\it n} is such that {\tt x}{\it n} is a -%fresh name. -The new subgoal is $U$. -% If the {\tt x} has been renamed {\tt x}{\it n} then it is replaced -% by {\tt x}{\it n} in {\tt U}. - -If the goal is a non dependent product {\tt $T$ -> $U$}, then it puts -in the local context either {\tt H}{\it n}{\tt :$T$} (if $T$ is of -type {\tt Set} or {\tt Prop}) or {\tt X}{\it n}{\tt :$T$} (if the type -of $T$ is {\tt Type}). The optional index {\it n} is such that {\tt -H}{\it n} or {\tt X}{\it n} is a fresh identifier. -In both cases the new subgoal is $U$. - -If the goal is neither a product nor starting with a let definition, -the tactic {\tt intro} applies the tactic {\tt red} until the tactic -{\tt intro} can be applied or the goal is not reducible. - -\begin{ErrMsgs} -\item \errindex{No product even after head-reduction} -\item \errindexbis{{\ident} is already used}{is already used} -\end{ErrMsgs} - -\begin{Variants} - -\item {\tt intros}\tacindex{intros} - - Repeats {\tt intro} until it meets the head-constant. It never reduces - head-constants and it never fails. - -\item {\tt intro {\ident}} - - Applies {\tt intro} but forces {\ident} to be the name of the - introduced hypothesis. - - \ErrMsg \errindex{name {\ident} is already used} - - \Rem If a name used by {\tt intro} hides the base name of a global - constant then the latter can still be referred to by a qualified name - (see \ref{LongNames}). - -\item {\tt intros \ident$_1$ \dots\ \ident$_n$} - - Is equivalent to the composed tactic {\tt intro \ident$_1$; \dots\ ; - intro \ident$_n$}. - - More generally, the \texttt{intros} tactic takes a pattern as - argument in order to introduce names for components of an inductive - definition or to clear introduced hypotheses; This is explained - in~\ref{intros-pattern}. - -\item {\tt intros until {\ident}} \tacindex{intros until} - - Repeats {\tt intro} until it meets a premise of the goal having form - {\tt (} {\ident}~{\tt :}~{\term} {\tt )} and discharges the variable - named {\ident} of the current goal. - - \ErrMsg \errindex{No such hypothesis in current goal} - -\item {\tt intros until {\num}} \tacindex{intros until} - - Repeats {\tt intro} until the {\num}-th non-dependent product. For - instance, on the subgoal % - \verb+forall x y:nat, x=y -> y=x+ the tactic \texttt{intros until 1} - is equivalent to \texttt{intros x y H}, as \verb+x=y -> y=x+ is the - first non-dependent product. And on the subgoal % - \verb+forall x y z:nat, x=y -> y=x+ the tactic \texttt{intros until 1} - is equivalent to \texttt{intros x y z} as the product on \texttt{z} - can be rewritten as a non-dependent product: % - \verb+forall x y:nat, nat -> x=y -> y=x+ - - - \ErrMsg \errindex{No such hypothesis in current goal} - - Happens when {\num} is 0 or is greater than the number of non-dependent - products of the goal. - -\item {\tt intro after \ident} \tacindex{intro after}\\ - {\tt intro before \ident} \tacindex{intro before}\\ - {\tt intro at top} \tacindex{intro at top}\\ - {\tt intro at bottom} \tacindex{intro at bottom} - - Applies {\tt intro} and moves the freshly introduced hypothesis - respectively after the hypothesis \ident{}, before the hypothesis - \ident{}, at the top of the local context, or at the bottom of the - local context. All hypotheses on which the new hypothesis depends - are moved too so as to respect the order of dependencies between - hypotheses. Note that {\tt intro at bottom} is a synonym for {\tt - intro} with no argument. - -\begin{ErrMsgs} -\item \errindex{No product even after head-reduction} -\item \errindex{No such hypothesis} : {\ident} -\end{ErrMsgs} - -\item {\tt intro \ident$_1$ after \ident$_2$}\\ - {\tt intro \ident$_1$ before \ident$_2$}\\ - {\tt intro \ident$_1$ at top}\\ - {\tt intro \ident$_1$ at bottom} - - Behaves as previously but naming the introduced hypothesis - \ident$_1$. It is equivalent to {\tt intro \ident$_1$} followed by - the appropriate call to {\tt move}~(see Section~\ref{move}). - -\begin{ErrMsgs} -\item \errindex{No product even after head-reduction} -\item \errindex{No such hypothesis} : {\ident} -\end{ErrMsgs} - -\end{Variants} - -\subsection{\tt apply \term -\tacindex{apply} -\label{apply}} - -This tactic applies to any goal. The argument {\term} is a term -well-formed in the local context. The tactic {\tt apply} tries to -match the current goal against the conclusion of the type of {\term}. -If it succeeds, then the tactic returns as many subgoals as the number -of non dependent premises of the type of {\term}. If the conclusion of -the type of {\term} does not match the goal {\em and} the conclusion -is an inductive type isomorphic to a tuple type, then each component -of the tuple is recursively matched to the goal in the left-to-right -order. - -The tactic {\tt apply} relies on first-order unification with -dependent types unless the conclusion of the type of {\term} is of the -form {\tt ($P$~ $t_1$~\ldots ~$t_n$)} with $P$ to be instantiated. In -the latter case, the behavior depends on the form of the goal. If the -goal is of the form {\tt (fun $x$ => $Q$)~$u_1$~\ldots~$u_n$} and the -$t_i$ and $u_i$ unifies, then $P$ is taken to be (fun $x$ => $Q$). -Otherwise, {\tt apply} tries to define $P$ by abstracting over -$t_1$~\ldots ~$t_n$ in the goal. See {\tt pattern} in -Section~\ref{pattern} to transform the goal so that it gets the form -{\tt (fun $x$ => $Q$)~$u_1$~\ldots~$u_n$}. - -\begin{ErrMsgs} -\item \errindex{Impossible to unify \dots\ with \dots} - - The {\tt apply} - tactic failed to match the conclusion of {\term} and the current goal. - You can help the {\tt apply} tactic by transforming your - goal with the {\tt change} or {\tt pattern} tactics (see - sections~\ref{pattern},~\ref{change}). - -\item \errindex{Unable to find an instance for the variables -{\ident} \ldots {\ident}} - - This occurs when some instantiations of the premises of {\term} are not - deducible from the unification. This is the case, for instance, when - you want to apply a transitivity property. In this case, you have to - use one of the variants below: - -\end{ErrMsgs} - -\begin{Variants} - -\item{\tt apply {\term} with {\term$_1$} \dots\ {\term$_n$}} - \tacindex{apply \dots\ with} - - Provides {\tt apply} with explicit instantiations for all dependent - premises of the type of {\term} which do not occur in the conclusion - and consequently cannot be found by unification. Notice that - {\term$_1$} \dots\ {\term$_n$} must be given according to the order - of these dependent premises of the type of {\term}. - - \ErrMsg \errindex{Not the right number of missing arguments} - -\item{\tt apply {\term} with ({\vref$_1$} := {\term$_1$}) \dots\ ({\vref$_n$} - := {\term$_n$})} - - This also provides {\tt apply} with values for instantiating - premises. Here, variables are referred by names and non-dependent - products by increasing numbers (see syntax in Section~\ref{Binding-list}). - -\item {\tt apply} {\term$_1$} {\tt ,} \ldots {\tt ,} {\term$_n$} - - This is a shortcut for {\tt apply} {\term$_1$} {\tt ; [ ..~|} - \ldots~{\tt ; [ ..~| {\tt apply} {\term$_n$} ]} \ldots~{\tt ]}, i.e. for the - successive applications of {\term$_{i+1}$} on the last subgoal - generated by {\tt apply} {\term$_i$}, starting from the application - of {\term$_1$}. - -\item {\tt eapply \term}\tacindex{eapply}\label{eapply} - - The tactic {\tt eapply} behaves as {\tt apply} but does not fail - when no instantiation are deducible for some variables in the - premises. Rather, it turns these variables into so-called - existential variables which are variables still to instantiate. An - existential variable is identified by a name of the form {\tt ?$n$} - where $n$ is a number. The instantiation is intended to be found - later in the proof. - - An example of use of {\tt eapply} is given in - Section~\ref{eapply-example}. - -\item {\tt simple apply {\term}} \tacindex{simple apply} - - This behaves like {\tt apply} but it reasons modulo conversion only - on subterms that contain no variables to instantiate. For instance, - if {\tt id := fun x:nat => x} and {\tt H : forall y, id y = y} then - {\tt simple apply H} on goal {\tt O = O} does not succeed because it - would require the conversion of {\tt f ?y} and {\tt O} where {\tt - ?y} is a variable to instantiate. Tactic {\tt simple apply} does not - either traverse tuples as {\tt apply} does. - - Because it reasons modulo a limited amount of conversion, {\tt - simple apply} fails quicker than {\tt apply} and it is then - well-suited for uses in used-defined tactics that backtrack often. - -\item \zeroone{{\tt simple}} {\tt apply} {\term$_1$} \zeroone{{\tt with} - {\bindinglist$_1$}} {\tt ,} \ldots {\tt ,} {\term$_n$} \zeroone{{\tt with} - {\bindinglist$_n$}}\\ - \zeroone{{\tt simple}} {\tt eapply} {\term$_1$} \zeroone{{\tt with} - {\bindinglist$_1$}} {\tt ,} \ldots {\tt ,} {\term$_n$} \zeroone{{\tt with} - {\bindinglist$_n$}} - - This summarizes the different syntaxes for {\tt apply} and {\tt eapply}. - -\item {\tt lapply {\term}} \tacindex{lapply} - - This tactic applies to any goal, say {\tt G}. The argument {\term} - has to be well-formed in the current context, its type being - reducible to a non-dependent product {\tt A -> B} with {\tt B} - possibly containing products. Then it generates two subgoals {\tt - B->G} and {\tt A}. Applying {\tt lapply H} (where {\tt H} has type - {\tt A->B} and {\tt B} does not start with a product) does the same - as giving the sequence {\tt cut B. 2:apply H.} where {\tt cut} is - described below. - - \Warning When {\term} contains more than one non - dependent product the tactic {\tt lapply} only takes into account the - first product. - -\end{Variants} - -\subsection{{\tt set ( {\ident} {\tt :=} {\term} \tt )} -\label{tactic:set} -\tacindex{set} -\tacindex{pose} -\tacindex{remember}} - -This replaces {\term} by {\ident} in the conclusion or in the -hypotheses of the current goal and adds the new definition {\ident -{\tt :=} \term} to the local context. The default is to make this -replacement only in the conclusion. - -\begin{Variants} - -\item {\tt set (} {\ident} {\tt :=} {\term} {\tt ) in {\occgoalset}} - -This notation allows to specify which occurrences of {\term} have to -be substituted in the context. The {\tt in {\occgoalset}} clause is an -occurrence clause whose syntax and behavior is described in -Section~\ref{Occurrences clauses}. - -\item {\tt set (} {\ident} \nelist{\binder}{} {\tt :=} {\term} {\tt )} - - This is equivalent to {\tt set (} {\ident} {\tt :=} {\tt fun} - \nelist{\binder}{} {\tt =>} {\term} {\tt )}. - -\item {\tt set } {\term} - - This behaves as {\tt set (} {\ident} := {\term} {\tt )} but {\ident} - is generated by {\Coq}. This variant also supports an occurrence clause. - -\item {\tt set (} {\ident$_0$} \nelist{\binder}{} {\tt :=} {\term} - {\tt ) in {\occgoalset}}\\ - {\tt set {\term} in {\occgoalset}} - - These are the general forms which combine the previous possibilities. - -\item {\tt remember {\term} {\tt as} {\ident}} - - This behaves as {\tt set (} {\ident} := {\term} {\tt ) in *} and using a - logical (Leibniz's) equality instead of a local definition. - -\item {\tt remember {\term} {\tt as} {\ident} in {\occgoalset}} - - This is a more general form of {\tt remember} that remembers the - occurrences of {\term} specified by an occurrences set. - -\item {\tt pose ( {\ident} {\tt :=} {\term} {\tt )}} - - This adds the local definition {\ident} := {\term} to the current - context without performing any replacement in the goal or in the - hypotheses. It is equivalent to {\tt set ( {\ident} {\tt :=} - {\term} {\tt ) in |-}}. - -\item {\tt pose (} {\ident} \nelist{\binder}{} {\tt :=} {\term} {\tt )} - - This is equivalent to {\tt pose (} {\ident} {\tt :=} {\tt fun} - \nelist{\binder}{} {\tt =>} {\term} {\tt )}. - -\item{\tt pose {\term}} - - This behaves as {\tt pose (} {\ident} := {\term} {\tt )} but - {\ident} is generated by {\Coq}. - -\end{Variants} - -\subsection{{\tt assert ( {\ident} : {\form} \tt )} -\tacindex{assert}} - -This tactic applies to any goal. {\tt assert (H : U)} adds a new -hypothesis of name \texttt{H} asserting \texttt{U} to the current goal -and opens a new subgoal \texttt{U}\footnote{This corresponds to the - cut rule of sequent calculus.}. The subgoal {\texttt U} comes first -in the list of subgoals remaining to prove. - -\begin{ErrMsgs} -\item \errindex{Not a proposition or a type} - - Arises when the argument {\form} is neither of type {\tt Prop}, {\tt - Set} nor {\tt Type}. - -\end{ErrMsgs} - -\begin{Variants} - -\item{\tt assert {\form}} - - This behaves as {\tt assert (} {\ident} : {\form} {\tt )} but - {\ident} is generated by {\Coq}. - -\item{\tt assert (} {\ident} := {\term} {\tt )} - - This behaves as {\tt assert ({\ident} : {\type});[exact - {\term}|idtac]} where {\type} is the type of {\term}. - -\item {\tt cut {\form}}\tacindex{cut} - - This tactic applies to any goal. It implements the non dependent - case of the ``App''\index{Typing rules!App} rule given in - Section~\ref{Typed-terms}. (This is Modus Ponens inference rule.) - {\tt cut U} transforms the current goal \texttt{T} into the two - following subgoals: {\tt U -> T} and \texttt{U}. The subgoal {\tt U - -> T} comes first in the list of remaining subgoal to prove. - -\item \texttt{assert {\form} by {\tac}}\tacindex{assert by} - - This tactic behaves like \texttt{assert} but applies {\tac} - to solve the subgoals generated by \texttt{assert}. - -\item \texttt{assert {\form} as {\intropattern}\tacindex{assert as}} - - If {\intropattern} is a naming introduction pattern (see - Section~\ref{intros-pattern}), the hypothesis is named after this - introduction pattern (in particular, if {\intropattern} is {\ident}, - the tactic behaves like \texttt{assert ({\ident} : {\form})}). - - If {\intropattern} is a disjunctive/conjunctive introduction - pattern, the tactic behaves like \texttt{assert {\form}} then destructing the - resulting hypothesis using the given introduction pattern. - -\item \texttt{assert {\form} as {\intropattern} by {\tac}} - - This combines the two previous variants of {\tt assert}. - -\item \texttt{pose proof {\term} as {\intropattern}\tacindex{pose proof}} - - This tactic behaves like \texttt{assert T as {\intropattern} by - exact {\term}} where \texttt{T} is the type of {\term}. - - In particular, \texttt{pose proof {\term} as {\ident}} behaves as - \texttt{assert ({\ident}:T) by exact {\term}} (where \texttt{T} is - the type of {\term}) and \texttt{pose proof {\term} as - {\disjconjintropattern}\tacindex{pose proof}} behaves - like \texttt{destruct {\term} as {\disjconjintropattern}}. - -\item {\tt specialize ({\ident} \term$_1$ {\ldots} \term$_n$)\tacindex{specialize}} \\ - {\tt specialize {\ident} with \bindinglist} - - The tactic {\tt specialize} works on local hypothesis \ident. - The premises of this hypothesis (either universal - quantifications or non-dependent implications) are instantiated - by concrete terms coming either from arguments \term$_1$ - $\ldots$ \term$_n$ or from a bindings list (see - Section~\ref{Binding-list} for more about bindings lists). In the - second form, all instantiation elements must be given, whereas - in the first form the application to \term$_1$ {\ldots} - \term$_n$ can be partial. The first form is equivalent to - {\tt assert (\ident':=\ident \term$_1$ {\ldots} \term$_n$); - clear \ident; rename \ident' into \ident}. - - The name {\ident} can also refer to a global lemma or - hypothesis. In this case, for compatibility reasons, the - behavior of {\tt specialize} is close to that of {\tt - generalize}: the instantiated statement becomes an additional - premise of the goal. - -%% Moreover, the old syntax allows the use of a number after {\tt specialize} -%% for controlling the number of premises to instantiate. Giving this -%% number should not be mandatory anymore (automatic detection of how -%% many premises can be eaten without leaving meta-variables). Hence -%% no documentation for this integer optional argument of specialize - -\end{Variants} - -\subsection{{\tt apply {\term} in {\ident}} -\tacindex{apply \ldots\ in}} - -This tactic applies to any goal. The argument {\term} is a term -well-formed in the local context and the argument {\ident} is an -hypothesis of the context. The tactic {\tt apply {\term} in {\ident}} -tries to match the conclusion of the type of {\ident} against a non -dependent premise of the type of {\term}, trying them from right to -left. If it succeeds, the statement of hypothesis {\ident} is -replaced by the conclusion of the type of {\term}. The tactic also -returns as many subgoals as the number of other non dependent premises -in the type of {\term} and of the non dependent premises of the type -of {\ident}. If the conclusion of the type of {\term} does not match -the goal {\em and} the conclusion is an inductive type isomorphic to a -tuple type, then the tuple is (recursively) decomposed and the first -component of the tuple of which a non dependent premise matches the -conclusion of the type of {\ident}. Tuples are decomposed in a -width-first left-to-right order (for instance if the type of {\tt H1} -is a \verb=A <-> B= statement, and the type of {\tt H2} is \verb=A= -then {\tt apply H1 in H2} transforms the type of {\tt H2} into {\tt - B}). The tactic {\tt apply} relies on first-order pattern-matching -with dependent types. - -\begin{ErrMsgs} -\item \errindex{Statement without assumptions} - -This happens if the type of {\term} has no non dependent premise. - -\item \errindex{Unable to apply} - -This happens if the conclusion of {\ident} does not match any of the -non dependent premises of the type of {\term}. -\end{ErrMsgs} - -\begin{Variants} -\item {\tt apply \nelist{\term}{,} in {\ident}} - -This applies each of {\term} in sequence in {\ident}. - -\item {\tt apply \nelist{{\term} with {\bindinglist}}{,} in {\ident}} - -This does the same but uses the bindings in each {\bindinglist} to -instantiate the parameters of the corresponding type of {\term} -(see syntax of bindings in Section~\ref{Binding-list}). - -\item {\tt eapply \nelist{{\term} with {\bindinglist}}{,} in {\ident}} -\tacindex{eapply {\ldots} in} - -This works as {\tt apply \nelist{{\term} with {\bindinglist}}{,} in -{\ident}} but turns unresolved bindings into existential variables, if -any, instead of failing. - -\item {\tt apply \nelist{{\term}{,} with {\bindinglist}}{,} in {\ident} as {\disjconjintropattern}} - -This works as {\tt apply \nelist{{\term}{,} with {\bindinglist}}{,} in -{\ident}} then destructs the hypothesis {\ident} along -{\disjconjintropattern} as {\tt destruct {\ident} as -{\disjconjintropattern}} would. - -\item {\tt eapply \nelist{{\term}{,} with {\bindinglist}}{,} in {\ident} as {\disjconjintropattern}} - -This works as {\tt apply \nelist{{\term}{,} with {\bindinglist}}{,} in {\ident} as {\disjconjintropattern}} but using {\tt eapply}. - -\item {\tt simple apply {\term} in {\ident}} -\tacindex{simple apply {\ldots} in} -\tacindex{simple eapply {\ldots} in} - -This behaves like {\tt apply {\term} in {\ident}} but it reasons -modulo conversion only on subterms that contain no variables to -instantiate. For instance, if {\tt id := fun x:nat => x} and {\tt H : - forall y, id y = y -> True} and {\tt H0 : O = O} then {\tt simple - apply H in H0} does not succeed because it would require the -conversion of {\tt f ?y} and {\tt O} where {\tt ?y} is a variable to -instantiate. Tactic {\tt simple apply {\term} in {\ident}} does not -either traverse tuples as {\tt apply {\term} in {\ident}} does. - -\item {\tt \zeroone{simple} apply \nelist{{\term} \zeroone{with {\bindinglist}}}{,} in {\ident} \zeroone{as {\disjconjintropattern}}}\\ -{\tt \zeroone{simple} eapply \nelist{{\term} \zeroone{with {\bindinglist}}}{,} in {\ident} \zeroone{as {\disjconjintropattern}}} - -This summarizes the different syntactic variants of {\tt apply {\term} - in {\ident}} and {\tt eapply {\term} in {\ident}}. -\end{Variants} - -\subsection{\tt generalize \term -\tacindex{generalize} -\label{generalize}} - -This tactic applies to any goal. It generalizes the conclusion w.r.t. -one subterm of it. For example: - -\begin{coq_eval} -Goal forall x y:nat, (0 <= x + y + y). -intros. -\end{coq_eval} -\begin{coq_example} -Show. -generalize (x + y + y). -\end{coq_example} - -\begin{coq_eval} -Abort. -\end{coq_eval} - -If the goal is $G$ and $t$ is a subterm of type $T$ in the goal, then -{\tt generalize} \textit{t} replaces the goal by {\tt forall (x:$T$), $G'$} -where $G'$ is obtained from $G$ by replacing all occurrences of $t$ by -{\tt x}. The name of the variable (here {\tt n}) is chosen based on $T$. - -\begin{Variants} -\item {\tt generalize {\term$_1$ , \dots\ , \term$_n$}} - - Is equivalent to {\tt generalize \term$_n$; \dots\ ; generalize - \term$_1$}. Note that the sequence of \term$_i$'s are processed - from $n$ to $1$. - -\item {\tt generalize {\term} at {\num$_1$ \dots\ \num$_i$}} - - Is equivalent to {\tt generalize \term} but generalizing only over - the specified occurrences of {\term} (counting from left to right on the - expression printed using option {\tt Set Printing All}). - -\item {\tt generalize {\term} as {\ident}} - - Is equivalent to {\tt generalize \term} but use {\ident} to name the - generalized hypothesis. - -\item {\tt generalize {\term$_1$} at {\num$_{11}$ \dots\ \num$_{1i_1}$} - as {\ident$_1$} - , {\ldots} , - {\term$_n$} at {\num$_{n1}$ \dots\ \num$_{ni_n}$} - as {\ident$_2$}} - - This is the most general form of {\tt generalize} that combines the - previous behaviors. - -\item {\tt generalize dependent \term} \tacindex{generalize dependent} - - This generalizes {\term} but also {\em all} hypotheses which depend - on {\term}. It clears the generalized hypotheses. - -\end{Variants} - - -\subsection{\tt revert \ident$_1$ \dots\ \ident$_n$ -\tacindex{revert} -\label{revert}} - -This applies to any goal with variables \ident$_1$ \dots\ \ident$_n$. -It moves the hypotheses (possibly defined) to the goal, if this respects -dependencies. This tactic is the inverse of {\tt intro}. - -\begin{ErrMsgs} -\item \errindexbis{{\ident} is used in the hypothesis {\ident'}}{is - used in the hypothesis} -\end{ErrMsgs} - -\begin{Variants} -\item {\tt revert dependent \ident \tacindex{revert dependent}} - - This moves to the goal the hypothesis \ident\ and all hypotheses - which depend on it. - -\end{Variants} - -\subsection{\tt change \term -\tacindex{change} -\label{change}} - -This tactic applies to any goal. It implements the rule -``Conv''\index{Typing rules!Conv} given in Section~\ref{Conv}. {\tt - change U} replaces the current goal \T\ with \U\ providing that -\U\ is well-formed and that \T\ and \U\ are convertible. - -\begin{ErrMsgs} -\item \errindex{Not convertible} -\end{ErrMsgs} - -\tacindex{change \dots\ in} -\begin{Variants} -\item {\tt change \term$_1$ with \term$_2$} - - This replaces the occurrences of \term$_1$ by \term$_2$ in the - current goal. The terms \term$_1$ and \term$_2$ must be - convertible. - -\item {\tt change \term$_1$ at \num$_1$ \dots\ \num$_i$ with \term$_2$} - - This replaces the occurrences numbered \num$_1$ \dots\ \num$_i$ of - \term$_1$ by \term$_2$ in the current goal. - The terms \term$_1$ and \term$_2$ must be convertible. - - \ErrMsg {\tt Too few occurrences} - -\item {\tt change {\term} in {\ident}} - -\item {\tt change \term$_1$ with \term$_2$ in {\ident}} - -\item {\tt change \term$_1$ at \num$_1$ \dots\ \num$_i$ with \term$_2$ in - {\ident}} - - This applies the {\tt change} tactic not to the goal but to the - hypothesis {\ident}. - -\end{Variants} - -\SeeAlso \ref{Conversion-tactics} - -\subsection{\tt fix {\ident} {\num} -\tacindex{fix} -\label{tactic:fix}} - -This tactic is a primitive tactic to start a proof by induction. In -general, it is easier to rely on higher-level induction tactics such -as the ones described in Section~\ref{Tac-induction}. - -In the syntax of the tactic, the identifier {\ident} is the name given -to the induction hypothesis. The natural number {\num} tells on which -premise of the current goal the induction acts, starting -from 1 and counting both dependent and non dependent -products. Especially, the current lemma must be composed of at least -{\num} products. - -Like in a {\tt fix} expression, the induction -hypotheses have to be used on structurally smaller arguments. -The verification that inductive proof arguments are correct is done -only at the time of registering the lemma in the environment. To know -if the use of induction hypotheses is correct at some -time of the interactive development of a proof, use the command {\tt - Guarded} (see Section~\ref{Guarded}). - -\begin{Variants} - \item {\tt fix} {\ident}$_1$ {\num} {\tt with (} {\ident}$_2$ - \nelist{{\binder}$_{2}$}{} \zeroone{{\tt \{ struct {\ident$'_2$} - \}}} {\tt :} {\type}$_2$ {\tt )} {\ldots} {\tt (} {\ident}$_1$ - \nelist{{\binder}$_n$}{} \zeroone{{\tt \{ struct {\ident$'_n$} \}}} - {\tt :} {\type}$_n$ {\tt )} - -This starts a proof by mutual induction. The statements to be -simultaneously proved are respectively {\tt forall} - \nelist{{\binder}$_2$}{}{\tt ,} {\type}$_2$, {\ldots}, {\tt forall} - \nelist{{\binder}$_n$}{}{\tt ,} {\type}$_n$. The identifiers -{\ident}$_1$ {\ldots} {\ident}$_n$ are the names of the induction -hypotheses. The identifiers {\ident}$'_2$ {\ldots} {\ident}$'_n$ are the -respective names of the premises on which the induction is performed -in the statements to be simultaneously proved (if not given, the -system tries to guess itself what they are). - -\end{Variants} - -\subsection{\tt cofix {\ident} -\tacindex{cofix} -\label{tactic:cofix}} - -This tactic starts a proof by coinduction. The identifier {\ident} is -the name given to the coinduction hypothesis. Like in a {\tt cofix} -expression, the use of induction hypotheses have to guarded by a -constructor. The verification that the use of coinductive hypotheses -is correct is done only at the time of registering the lemma in the -environment. To know if the use of coinduction hypotheses is correct -at some time of the interactive development of a proof, use the -command {\tt Guarded} (see Section~\ref{Guarded}). - - -\begin{Variants} - \item {\tt cofix} {\ident}$_1$ {\tt with (} {\ident}$_2$ - \nelist{{\binder}$_2$}{} {\tt :} {\type}$_2$ {\tt )} {\ldots} {\tt - (} {\ident}$_1$ \nelist{{\binder}$_1$}{} {\tt :} {\type}$_n$ - {\tt )} - -This starts a proof by mutual coinduction. The statements to be -simultaneously proved are respectively {\tt forall} -\nelist{{\binder}$_2$}{}{\tt ,} {\type}$_2$, {\ldots}, {\tt forall} - \nelist{{\binder}$_n$}{}{\tt ,} {\type}$_n$. The identifiers - {\ident}$_1$ {\ldots} {\ident}$_n$ are the names of the - coinduction hypotheses. - -\end{Variants} - -\subsection{\tt evar (\ident:\term) -\tacindex{evar} -\label{evar}} - -The {\tt evar} tactic creates a new local definition named \ident\ with -type \term\ in the context. The body of this binding is a fresh -existential variable. - -\subsection{\tt instantiate (\num:= \term) -\tacindex{instantiate} -\label{instantiate}} - -The {\tt instantiate} tactic allows to solve an existential variable -with the term \term. The \num\ argument is the position of the -existential variable from right to left in the conclusion. This cannot be -the number of the existential variable since this number is different -in every session. - -\begin{Variants} - \item {\tt instantiate (\num:=\term) in \ident} - - \item {\tt instantiate (\num:=\term) in (Value of \ident)} - - \item {\tt instantiate (\num:=\term) in (Type of \ident)} - -These allow to refer respectively to existential variables occurring in -a hypothesis or in the body or the type of a local definition. - - \item {\tt instantiate} - - Without argument, the {\tt instantiate} tactic tries to solve as - many existential variables as possible, using information gathered - from other tactics in the same tactical. This is automatically - done after each complete tactic (i.e. after a dot in proof mode), - but not, for example, between each tactic when they are sequenced - by semicolons. - -\end{Variants} - -\subsection{\tt admit -\tacindex{admit} -\label{admit}} - -The {\tt admit} tactic ``solves'' the current subgoal by an -axiom. This typically allows to temporarily skip a subgoal so as to -progress further in the rest of the proof. To know if some proof still -relies on unproved subgoals, one can use the command {\tt Print -Assumptions} (see Section~\ref{PrintAssumptions}). Admitted subgoals -have names of the form {\ident}\texttt{\_admitted} possibly followed -by a number. - -\subsection{\tt constr\_eq \term$_1$ \term$_2$ -\tacindex{constr\_eq} -\label{constreq}} - -This tactic applies to any goal. It checks whether its arguments are -equal modulo alpha conversion and casts. - -\ErrMsg \errindex{Not equal} - -\subsection{\tt is\_evar \term -\tacindex{is\_evar} -\label{isevar}} - -This tactic applies to any goal. It checks whether its argument is an -existential variable. Existential variables are uninstantiated -variables generated by e.g. {\tt eapply} (see Section~\ref{apply}). - -\ErrMsg \errindex{Not an evar} - -\subsection{\tt has\_evar \term -\tacindex{has\_evar} -\label{hasevar}} - -This tactic applies to any goal. It checks whether its argument has an -existential variable as a subterm. Unlike {\tt context} patterns -combined with {\tt is\_evar}, this tactic scans all subterms, -including those under binders. - -\ErrMsg \errindex{No evars} - -\subsection{\tt is\_var \term -\tacindex{is\_var} -\label{isvar}} - -This tactic applies to any goal. It checks whether its argument is a -variable or hypothesis in the current goal context or in the opened sections. - -\ErrMsg \errindex{Not a variable or hypothesis} - -\subsection{Bindings list -\index{Binding list} -\label{Binding-list}} - -Tactics that take a term as argument may also support a bindings list, so -as to instantiate some parameters of the term by name or position. -The general form of a term equipped with a bindings list is {\tt -{\term} with {\bindinglist}} where {\bindinglist} may be of two -different forms: - -\begin{itemize} -\item In a bindings list of the form {\tt (\vref$_1$ := \term$_1$) - \dots\ (\vref$_n$ := \term$_n$)}, {\vref} is either an {\ident} or a - {\num}. The references are determined according to the type of - {\term}. If \vref$_i$ is an identifier, this identifier has to be - bound in the type of {\term} and the binding provides the tactic - with an instance for the parameter of this name. If \vref$_i$ is - some number $n$, this number denotes the $n$-th non dependent - premise of the {\term}, as determined by the type of {\term}. - - \ErrMsg \errindex{No such binder} - -\item A bindings list can also be a simple list of terms {\tt - \term$_1$ \dots\term$_n$}. In that case the references to - which these terms correspond are determined by the tactic. In case - of {\tt induction}, {\tt destruct}, {\tt elim} and {\tt case} (see - Section~\ref{elim}) the terms have to provide instances for all the - dependent products in the type of \term\ while in the case of {\tt - apply}, or of {\tt constructor} and its variants, only instances for - the dependent products which are not bound in the conclusion of the - type are required. - - \ErrMsg \errindex{Not the right number of missing arguments} -\end{itemize} - -\subsection{Occurrences sets and occurrences clauses} -\label{Occurrences clauses} -\index{Occurrences clauses} - -An occurrences clause is a modifier to some tactics that obeys the -following syntax: - -$\!\!\!$\begin{tabular}{lcl} -{\occclause} & ::= & {\tt in} {\occgoalset} \\ -{\occgoalset} & ::= & - \zeroone{{\ident$_1$} \zeroone{\atoccurrences} {\tt ,} \\ -& & {\dots} {\tt ,}\\ -& & {\ident$_m$} \zeroone{\atoccurrences}}\\ -& & \zeroone{{\tt |-} \zeroone{{\tt *} \zeroone{\atoccurrences}}}\\ -& | & - {\tt *} {\tt |-} \zeroone{{\tt *} \zeroone{\atoccurrences}}\\ -& | & - {\tt *}\\ -{\atoccurrences} & ::= & {\tt at} {\occlist}\\ -{\occlist} & ::= & \zeroone{{\tt -}} {\num$_1$} \dots\ {\num$_n$} -\end{tabular} - -The role of an occurrence clause is to select a set of occurrences of -a {\term} in a goal. In the first case, the {{\ident$_i$} -\zeroone{{\tt at} {\num$_1^i$} \dots\ {\num$_{n_i}^i$}}} parts -indicate that occurrences have to be selected in the hypotheses named -{\ident$_i$}. If no numbers are given for hypothesis {\ident$_i$}, -then all occurrences of {\term} in the hypothesis are selected. If -numbers are given, they refer to occurrences of {\term} when the term -is printed using option {\tt Set Printing All} (see -Section~\ref{SetPrintingAll}), counting from left to right. In -particular, occurrences of {\term} in implicit arguments (see -Section~\ref{Implicit Arguments}) or coercions (see -Section~\ref{Coercions}) are counted. - -If a minus sign is given between {\tt at} and the list of occurrences, -it negates the condition so that the clause denotes all the occurrences except -the ones explicitly mentioned after the minus sign. - -As an exception to the left-to-right order, the occurrences in the -{\tt return} subexpression of a {\tt match} are considered {\em -before} the occurrences in the matched term. - -In the second case, the {\tt *} on the left of {\tt |-} means that -all occurrences of {\term} are selected in every hypothesis. - -In the first and second case, if {\tt *} is mentioned on the right of -{\tt |-}, the occurrences of the conclusion of the goal have to be -selected. If some numbers are given, then only the occurrences denoted -by these numbers are selected. In no numbers are given, all -occurrences of {\term} in the goal are selected. - -Finally, the last notation is an abbreviation for {\tt * |- *}. Note -also that {\tt |-} is optional in the first case when no {\tt *} is -given. - -Here are some tactics that understand occurrences clauses: -{\tt set}, {\tt remember}, {\tt induction}, {\tt destruct}. - -\SeeAlso~Sections~\ref{tactic:set}, \ref{Tac-induction}, \ref{SetPrintingAll}. - - -\section{Negation and contradiction} - -\subsection{\tt absurd \term -\tacindex{absurd} -\label{absurd}} - -This tactic applies to any goal. The argument {\term} is any -proposition {\tt P} of type {\tt Prop}. This tactic applies {\tt - False} elimination, that is it deduces the current goal from {\tt - False}, and generates as subgoals {\tt $\sim$P} and {\tt P}. It is -very useful in proofs by cases, where some cases are impossible. In -most cases, \texttt{P} or $\sim$\texttt{P} is one of the hypotheses of -the local context. - -\subsection{\tt contradiction -\label{contradiction} -\tacindex{contradiction}} - -This tactic applies to any goal. The {\tt contradiction} tactic -attempts to find in the current context (after all {\tt intros}) one -hypothesis which is equivalent to {\tt False}. It permits to prune -irrelevant cases. This tactic is a macro for the tactics sequence -{\tt intros; elimtype False; assumption}. - -\begin{ErrMsgs} -\item \errindex{No such assumption} -\end{ErrMsgs} - -\begin{Variants} -\item {\tt contradiction \ident} - -The proof of {\tt False} is searched in the hypothesis named \ident. -\end{Variants} - -\subsection {\tt contradict \ident} -\label{contradict} -\tacindex{contradict} - -This tactic allows to manipulate negated hypothesis and goals. The -name \ident\ should correspond to a hypothesis. With -{\tt contradict H}, the current goal and context is transformed in -the following way: -\begin{itemize} -\item {\tt H:$\neg$A $\vd$ B} \ becomes \ {\tt $\vd$ A} -\item {\tt H:$\neg$A $\vd$ $\neg$B} \ becomes \ {\tt H: B $\vd$ A } -\item {\tt H: A $\vd$ B} \ becomes \ {\tt $\vd$ $\neg$A} -\item {\tt H: A $\vd$ $\neg$B} \ becomes \ {\tt H: B $\vd$ $\neg$A} -\end{itemize} - -\subsection{\tt exfalso} -\label{exfalso} -\tacindex{exfalso} - -This tactic implements the ``ex falso quodlibet'' logical principle: -an elimination of {\tt False} is performed on the current goal, and the -user is then required to prove that {\tt False} is indeed provable in -the current context. This tactic is a macro for {\tt elimtype False}. - -\section{Conversion tactics -\index{Conversion tactics} -\label{Conversion-tactics}} - -This set of tactics implements different specialized usages of the -tactic \texttt{change}. - -All conversion tactics (including \texttt{change}) can be -parameterized by the parts of the goal where the conversion can -occur. This is done using \emph{goal clauses} which consists in a list -of hypotheses and, optionally, of a reference to the conclusion of the -goal. For defined hypothesis it is possible to specify if the -conversion should occur on the type part, the body part or both -(default). - -\index{Clauses} -\index{Goal clauses} -Goal clauses are written after a conversion tactic (tactics -\texttt{set}~\ref{tactic:set}, \texttt{rewrite}~\ref{rewrite}, -\texttt{replace}~\ref{tactic:replace} and -\texttt{autorewrite}~\ref{tactic:autorewrite} also use goal clauses) and -are introduced by the keyword \texttt{in}. If no goal clause is provided, -the default is to perform the conversion only in the conclusion. - -The syntax and description of the various goal clauses is the following: -\begin{description} -\item[]\texttt{in {\ident}$_1$ $\ldots$ {\ident}$_n$ |- } only in hypotheses {\ident}$_1$ - \ldots {\ident}$_n$ -\item[]\texttt{in {\ident}$_1$ $\ldots$ {\ident}$_n$ |- *} in hypotheses {\ident}$_1$ \ldots - {\ident}$_n$ and in the conclusion -\item[]\texttt{in * |-} in every hypothesis -\item[]\texttt{in *} (equivalent to \texttt{in * |- *}) everywhere -\item[]\texttt{in (type of {\ident}$_1$) (value of {\ident}$_2$) $\ldots$ |-} in - type part of {\ident}$_1$, in the value part of {\ident}$_2$, etc. -\end{description} - -For backward compatibility, the notation \texttt{in}~{\ident}$_1$\ldots {\ident}$_n$ -performs the conversion in hypotheses {\ident}$_1$\ldots {\ident}$_n$. - -%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -%voir reduction__conv_x : histoires d'univers. -%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% - -\subsection[{\tt cbv \flag$_1$ \dots\ \flag$_n$}, {\tt lazy \flag$_1$ -\dots\ \flag$_n$} and {\tt compute}] -{{\tt cbv \flag$_1$ \dots\ \flag$_n$}, {\tt lazy \flag$_1$ -\dots\ \flag$_n$} and {\tt compute} -\tacindex{cbv} -\tacindex{lazy} -\tacindex{compute} -\tacindex{vm\_compute}\label{vmcompute}} - -These parameterized reduction tactics apply to any goal and perform -the normalization of the goal according to the specified flags. In -correspondence with the kinds of reduction considered in \Coq\, namely -$\beta$ (reduction of functional application), $\delta$ (unfolding of -transparent constants, see \ref{Transparent}), $\iota$ (reduction of -pattern-matching over a constructed term, and unfolding of {\tt fix} -and {\tt cofix} expressions) and $\zeta$ (contraction of local -definitions), the flag are either {\tt beta}, {\tt delta}, {\tt iota} -or {\tt zeta}. The {\tt delta} flag itself can be refined into {\tt -delta [\qualid$_1$\ldots\qualid$_k$]} or {\tt delta --[\qualid$_1$\ldots\qualid$_k$]}, restricting in the first case the -constants to unfold to the constants listed, and restricting in the -second case the constant to unfold to all but the ones explicitly -mentioned. Notice that the {\tt delta} flag does not apply to -variables bound by a let-in construction inside the term itself (use -here the {\tt zeta} flag). In any cases, opaque constants are not -unfolded (see Section~\ref{Opaque}). - -The goal may be normalized with two strategies: {\em lazy} ({\tt lazy} -tactic), or {\em call-by-value} ({\tt cbv} tactic). The lazy strategy -is a call-by-need strategy, with sharing of reductions: the arguments of a -function call are partially evaluated only when necessary, and if an -argument is used several times then it is computed only once. This -reduction is efficient for reducing expressions with dead code. For -instance, the proofs of a proposition {\tt exists~$x$. $P(x)$} reduce to a -pair of a witness $t$, and a proof that $t$ satisfies the predicate -$P$. Most of the time, $t$ may be computed without computing the proof -of $P(t)$, thanks to the lazy strategy. - -The call-by-value strategy is the one used in ML languages: the -arguments of a function call are evaluated first, using a weak -reduction (no reduction under the $\lambda$-abstractions). Despite the -lazy strategy always performs fewer reductions than the call-by-value -strategy, the latter is generally more efficient for evaluating purely -computational expressions (i.e. with few dead code). - -\begin{Variants} -\item {\tt compute} \tacindex{compute}\\ - {\tt cbv} - - These are synonyms for {\tt cbv beta delta iota zeta}. - -\item {\tt lazy} - - This is a synonym for {\tt lazy beta delta iota zeta}. - -\item {\tt compute [\qualid$_1$\ldots\qualid$_k$]}\\ - {\tt cbv [\qualid$_1$\ldots\qualid$_k$]} - - These are synonyms of {\tt cbv beta delta - [\qualid$_1$\ldots\qualid$_k$] iota zeta}. - -\item {\tt compute -[\qualid$_1$\ldots\qualid$_k$]}\\ - {\tt cbv -[\qualid$_1$\ldots\qualid$_k$]} - - These are synonyms of {\tt cbv beta delta - -[\qualid$_1$\ldots\qualid$_k$] iota zeta}. - -\item {\tt lazy [\qualid$_1$\ldots\qualid$_k$]}\\ - {\tt lazy -[\qualid$_1$\ldots\qualid$_k$]} - - These are respectively synonyms of {\tt cbv beta delta - [\qualid$_1$\ldots\qualid$_k$] iota zeta} and {\tt cbv beta delta - -[\qualid$_1$\ldots\qualid$_k$] iota zeta}. - -\item {\tt vm\_compute} \tacindex{vm\_compute} - - This tactic evaluates the goal using the optimized call-by-value - evaluation bytecode-based virtual machine. This algorithm is - dramatically more efficient than the algorithm used for the {\tt - cbv} tactic, but it cannot be fine-tuned. It is specially - interesting for full evaluation of algebraic objects. This includes - the case of reflexion-based tactics. - -\end{Variants} - -% Obsolete? Anyway not very important message -%\begin{ErrMsgs} -%\item \errindex{Delta must be specified before} -% -% A list of constants appeared before the {\tt delta} flag. -%\end{ErrMsgs} - - -\subsection{{\tt red} -\tacindex{red}} - -This tactic applies to a goal which has the form {\tt - forall (x:T1)\dots(xk:Tk), c t1 \dots\ tn} where {\tt c} is a constant. If -{\tt c} is transparent then it replaces {\tt c} with its definition -(say {\tt t}) and then reduces {\tt (t t1 \dots\ tn)} according to -$\beta\iota\zeta$-reduction rules. - -\begin{ErrMsgs} -\item \errindex{Not reducible} -\end{ErrMsgs} - -\subsection{{\tt hnf} -\tacindex{hnf}} - -This tactic applies to any goal. It replaces the current goal with its -head normal form according to the $\beta\delta\iota\zeta$-reduction -rules, i.e. it reduces the head of the goal until it becomes a -product or an irreducible term. - -\Example -The term \verb+forall n:nat, (plus (S n) (S n))+ is not reduced by {\tt hnf}. - -\Rem The $\delta$ rule only applies to transparent constants -(see Section~\ref{Opaque} on transparency and opacity). - -\subsection{\tt simpl -\tacindex{simpl}} - -This tactic applies to any goal. The tactic {\tt simpl} first applies -$\beta\iota$-reduction rule. Then it expands transparent constants -and tries to reduce {\tt T'} according, once more, to $\beta\iota$ -rules. But when the $\iota$ rule is not applicable then possible -$\delta$-reductions are not applied. For instance trying to use {\tt -simpl} on {\tt (plus n O)=n} changes nothing. Notice that only -transparent constants whose name can be reused as such in the -recursive calls are possibly unfolded. For instance a constant defined -by {\tt plus' := plus} is possibly unfolded and reused in the -recursive calls, but a constant such as {\tt succ := plus (S O)} is -never unfolded. - -\tacindex{simpl \dots\ in} -\begin{Variants} -\item {\tt simpl {\term}} - - This applies {\tt simpl} only to the occurrences of {\term} in the - current goal. - -\item {\tt simpl {\term} at \num$_1$ \dots\ \num$_i$} - - This applies {\tt simpl} only to the \num$_1$, \dots, \num$_i$ - occurrences of {\term} in the current goal. - - \ErrMsg {\tt Too few occurrences} - -\item {\tt simpl {\ident}} - - This applies {\tt simpl} only to the applicative subterms whose head - occurrence is {\ident}. - -\item {\tt simpl {\ident} at \num$_1$ \dots\ \num$_i$} - - This applies {\tt simpl} only to the \num$_1$, \dots, \num$_i$ -applicative subterms whose head occurrence is {\ident}. - -\end{Variants} - -\subsection{\tt unfold \qualid -\tacindex{unfold} -\label{unfold}} - -This tactic applies to any goal. The argument {\qualid} must denote a -defined transparent constant or local definition (see Sections~\ref{Basic-definitions} and~\ref{Transparent}). The tactic {\tt - unfold} applies the $\delta$ rule to each occurrence of the constant -to which {\qualid} refers in the current goal and then replaces it -with its $\beta\iota$-normal form. - -\begin{ErrMsgs} -\item {\qualid} \errindex{does not denote an evaluable constant} - -\end{ErrMsgs} - -\begin{Variants} -\item {\tt unfold {\qualid}$_1$, \dots, \qualid$_n$} - \tacindex{unfold \dots\ in} - - Replaces {\em simultaneously} {\qualid}$_1$, \dots, {\qualid}$_n$ - with their definitions and replaces the current goal with its - $\beta\iota$ normal form. - -\item {\tt unfold {\qualid}$_1$ at \num$_1^1$, \dots, \num$_i^1$, -\dots,\ \qualid$_n$ at \num$_1^n$ \dots\ \num$_j^n$} - - The lists \num$_1^1$, \dots, \num$_i^1$ and \num$_1^n$, \dots, - \num$_j^n$ specify the occurrences of {\qualid}$_1$, \dots, - \qualid$_n$ to be unfolded. Occurrences are located from left to - right. - - \ErrMsg {\tt bad occurrence number of {\qualid}$_i$} - - \ErrMsg {\qualid}$_i$ {\tt does not occur} - -\item {\tt unfold {\qstring}} - - If {\qstring} denotes the discriminating symbol of a notation (e.g. {\tt - "+"}) or an expression defining a notation (e.g. \verb!"_ + _"!), and - this notation refers to an unfoldable constant, then the tactic - unfolds it. - -\item {\tt unfold {\qstring}\%{\delimkey}} - - This is variant of {\tt unfold {\qstring}} where {\qstring} gets its - interpretation from the scope bound to the delimiting key - {\delimkey} instead of its default interpretation (see - Section~\ref{scopechange}). - -\item {\tt unfold \qualidorstring$_1$ at \num$_1^1$, \dots, \num$_i^1$, -\dots,\ \qualidorstring$_n$ at \num$_1^n$ \dots\ \num$_j^n$} - - This is the most general form, where {\qualidorstring} is either a - {\qualid} or a {\qstring} referring to a notation. - -\end{Variants} - -\subsection{{\tt fold} \term -\tacindex{fold}} - -This tactic applies to any goal. The term \term\ is reduced using the {\tt red} -tactic. Every occurrence of the resulting term in the goal is then -replaced by \term. - -\begin{Variants} -\item {\tt fold} \term$_1$ \dots\ \term$_n$ - - Equivalent to {\tt fold} \term$_1${\tt;}\ldots{\tt; fold} \term$_n$. -\end{Variants} - -\subsection{{\tt pattern {\term}} -\tacindex{pattern} -\label{pattern}} - -This command applies to any goal. The argument {\term} must be a free -subterm of the current goal. The command {\tt pattern} performs -$\beta$-expansion (the inverse of $\bt$-reduction) of the current goal -(say \T) by -\begin{enumerate} -\item replacing all occurrences of {\term} in {\T} with a fresh variable -\item abstracting this variable -\item applying the abstracted goal to {\term} -\end{enumerate} - -For instance, if the current goal $T$ is expressible has $\phi(t)$ -where the notation captures all the instances of $t$ in $\phi(t)$, -then {\tt pattern $t$} transforms it into {\tt (fun x:$A$ => $\phi(${\tt -x}$)$) $t$}. This command can be used, for instance, when the tactic -{\tt apply} fails on matching. - -\begin{Variants} -\item {\tt pattern {\term} at {\num$_1$} \dots\ {\num$_n$}} - - Only the occurrences {\num$_1$} \dots\ {\num$_n$} of {\term} are - considered for $\beta$-expansion. Occurrences are located from left - to right. - -\item {\tt pattern {\term} at - {\num$_1$} \dots\ {\num$_n$}} - - All occurrences except the occurrences of indexes {\num$_1$} \dots\ - {\num$_n$} of {\term} are considered for - $\beta$-expansion. Occurrences are located from left to right. - -\item {\tt pattern {\term$_1$}, \dots, {\term$_m$}} - - Starting from a goal $\phi(t_1 \dots\ t_m)$, the tactic - {\tt pattern $t_1$, \dots,\ $t_m$} generates the equivalent goal {\tt - (fun (x$_1$:$A_1$) \dots\ (x$_m$:$A_m$) => $\phi(${\tt x$_1$\dots\ - x$_m$}$)$) $t_1$ \dots\ $t_m$}.\\ If $t_i$ occurs in one of the - generated types $A_j$ these occurrences will also be considered and - possibly abstracted. - -\item {\tt pattern {\term$_1$} at {\num$_1^1$} \dots\ {\num$_{n_1}^1$}, \dots, - {\term$_m$} at {\num$_1^m$} \dots\ {\num$_{n_m}^m$}} - - This behaves as above but processing only the occurrences \num$_1^1$, - \dots, \num$_i^1$ of \term$_1$, \dots, \num$_1^m$, \dots, \num$_j^m$ - of \term$_m$ starting from \term$_m$. - -\item {\tt pattern} {\term$_1$} \zeroone{{\tt at \zeroone{-}} {\num$_1^1$} \dots\ {\num$_{n_1}^1$}} {\tt ,} \dots {\tt ,} - {\term$_m$} \zeroone{{\tt at \zeroone{-}} {\num$_1^m$} \dots\ {\num$_{n_m}^m$}} - - This is the most general syntax that combines the different variants. - -\end{Variants} - -\subsection{Conversion tactics applied to hypotheses} - -{\convtactic} {\tt in} \ident$_1$ \dots\ \ident$_n$ - -Applies the conversion tactic {\convtactic} to the -hypotheses \ident$_1$, \ldots, \ident$_n$. The tactic {\convtactic} is -any of the conversion tactics listed in this section. - -If \ident$_i$ is a local definition, then \ident$_i$ can be replaced -by (Type of \ident$_i$) to address not the body but the type of the -local definition. Example: {\tt unfold not in (Type of H1) (Type of H3).} - -\begin{ErrMsgs} -\item \errindex{No such hypothesis} : {\ident}. -\end{ErrMsgs} - - -\section{Introductions} - -Introduction tactics address goals which are inductive constants. -They are used when one guesses that the goal can be obtained with one -of its constructors' type. - -\subsection{\tt constructor \num -\label{constructor} -\tacindex{constructor}} - -This tactic applies to a goal such that the head of its conclusion is -an inductive constant (say {\tt I}). The argument {\num} must be less -or equal to the numbers of constructor(s) of {\tt I}. Let {\tt ci} be -the {\tt i}-th constructor of {\tt I}, then {\tt constructor i} is -equivalent to {\tt intros; apply ci}. - -\begin{ErrMsgs} -\item \errindex{Not an inductive product} -\item \errindex{Not enough constructors} -\end{ErrMsgs} - -\begin{Variants} -\item \texttt{constructor} - - This tries \texttt{constructor 1} then \texttt{constructor 2}, - \dots\ , then \texttt{constructor} \textit{n} where \textit{n} if - the number of constructors of the head of the goal. - -\item {\tt constructor \num~with} {\bindinglist} - - Let {\tt ci} be the {\tt i}-th constructor of {\tt I}, then {\tt - constructor i with \bindinglist} is equivalent to {\tt intros; - apply ci with \bindinglist}. - - \Warning the terms in the \bindinglist\ are checked - in the context where {\tt constructor} is executed and not in the - context where {\tt apply} is executed (the introductions are not - taken into account). - -% To document? -% \item {\tt constructor {\tactic}} - -\item {\tt split}\tacindex{split} - - Applies if {\tt I} has only one constructor, typically in the case - of conjunction $A\land B$. Then, it is equivalent to {\tt constructor 1}. - -\item {\tt exists {\bindinglist}}\tacindex{exists} - - Applies if {\tt I} has only one constructor, for instance in the - case of existential quantification $\exists x\cdot P(x)$. - Then, it is equivalent to {\tt intros; constructor 1 with \bindinglist}. - -\item {\tt exists \nelist{\bindinglist}{,}} - - This iteratively applies {\tt exists {\bindinglist}}. - -\item {\tt left}\tacindex{left}\\ - {\tt right}\tacindex{right} - - Apply if {\tt I} has two constructors, for instance in the case of - disjunction $A\lor B$. Then, they are respectively equivalent to {\tt - constructor 1} and {\tt constructor 2}. - -\item {\tt left with \bindinglist}\\ - {\tt right with \bindinglist}\\ - {\tt split with \bindinglist} - - As soon as the inductive type has the right number of constructors, - these expressions are equivalent to calling {\tt - constructor $i$ with \bindinglist} for the appropriate $i$. - -\item \texttt{econstructor}\tacindex{econstructor}\\ - \texttt{eexists}\tacindex{eexists}\\ - \texttt{esplit}\tacindex{esplit}\\ - \texttt{eleft}\tacindex{eleft}\\ - \texttt{eright}\tacindex{eright}\\ - - These tactics and their variants behave like \texttt{constructor}, - \texttt{exists}, \texttt{split}, \texttt{left}, \texttt{right} and - their variants but they introduce existential variables instead of - failing when the instantiation of a variable cannot be found (cf - \texttt{eapply} and Section~\ref{eapply-example}). - -\end{Variants} - -\section[Induction and Case Analysis]{Induction and Case Analysis -\label{Tac-induction}} - -The tactics presented in this section implement induction or case -analysis on inductive or coinductive objects (see -Section~\ref{Cic-inductive-definitions}). - -\subsection{\tt induction \term -\tacindex{induction}} - -This tactic applies to any goal. The type of the argument {\term} must -be an inductive constant. Then, the tactic {\tt induction} -generates subgoals, one for each possible form of {\term}, i.e. one -for each constructor of the inductive type. - -The tactic {\tt induction} automatically replaces every occurrences -of {\term} in the conclusion and the hypotheses of the goal. It -automatically adds induction hypotheses (using names of the form {\tt - IHn1}) to the local context. If some hypothesis must not be taken -into account in the induction hypothesis, then it needs to be removed -first (you can also use the tactics {\tt elim} or {\tt simple induction}, -see below). - -There are particular cases: - -\begin{itemize} - -\item If {\term} is an identifier {\ident} denoting a quantified -variable of the conclusion of the goal, then {\tt induction {\ident}} -behaves as {\tt intros until {\ident}; induction {\ident}}. - -\item If {\term} is a {\num}, then {\tt induction {\num}} behaves as -{\tt intros until {\num}} followed by {\tt induction} applied to the -last introduced hypothesis. - -\Rem For simple induction on a numeral, use syntax {\tt induction -({\num})} (not very interesting anyway). - -\end{itemize} - -\Example - -\begin{coq_example} -Lemma induction_test : forall n:nat, n = n -> n <= n. -intros n H. -induction n. -\end{coq_example} - -\begin{ErrMsgs} -\item \errindex{Not an inductive product} -\item \errindex{Unable to find an instance for the variables -{\ident} \ldots {\ident}} - - Use in this case - the variant {\tt elim \dots\ with \dots} below. -\end{ErrMsgs} - -\begin{Variants} -\item{\tt induction {\term} as {\disjconjintropattern}} - - This behaves as {\tt induction {\term}} but uses the names in - {\disjconjintropattern} to name the variables introduced in the context. - The {\disjconjintropattern} must typically be of the form - {\tt [} $p_{11}$ \ldots - $p_{1n_1}$ {\tt |} {\ldots} {\tt |} $p_{m1}$ \ldots $p_{mn_m}$ {\tt - ]} with $m$ being the number of constructors of the type of - {\term}. Each variable introduced by {\tt induction} in the context - of the $i^{th}$ goal gets its name from the list $p_{i1}$ \ldots - $p_{in_i}$ in order. If there are not enough names, {\tt induction} - invents names for the remaining variables to introduce. More - generally, the $p_{ij}$ can be any disjunctive/conjunctive - introduction pattern (see Section~\ref{intros-pattern}). For instance, - for an inductive type with one constructor, the pattern notation - {\tt ($p_{1}$,\ldots,$p_{n}$)} can be used instead of - {\tt [} $p_{1}$ \ldots $p_{n}$ {\tt ]}. - -\item{\tt induction {\term} as {\namingintropattern}} - - This behaves as {\tt induction {\term}} but adds an equation between - {\term} and the value that {\term} takes in each of the induction - case. The name of the equation is built according to - {\namingintropattern} which can be an identifier, a ``?'', etc, as - indicated in Section~\ref{intros-pattern}. - -\item{\tt induction {\term} as {\namingintropattern} {\disjconjintropattern}} - - This combines the two previous forms. - -\item{\tt induction {\term} with \bindinglist} - - This behaves like \texttt{induction {\term}} providing explicit - instances for the premises of the type of {\term} (see the syntax of - bindings in Section~\ref{Binding-list}). - -\item{\tt einduction {\term}\tacindex{einduction}} - - This tactic behaves like \texttt{induction {\term}} excepts that it - does not fail if some dependent premise of the type of {\term} is - not inferable. Instead, the unresolved premises are posed as - existential variables to be inferred later, in the same way as {\tt - eapply} does (see Section~\ref{eapply-example}). - -\item {\tt induction {\term$_1$} using {\term$_2$}} - - This behaves as {\tt induction {\term$_1$}} but using {\term$_2$} as - induction scheme. It does not expect the conclusion of the type of - {\term$_1$} to be inductive. - -\item {\tt induction {\term$_1$} using {\term$_2$} with {\bindinglist}} - - This behaves as {\tt induction {\term$_1$} using {\term$_2$}} but - also providing instances for the premises of the type of {\term$_2$}. - -\item \texttt{induction {\term}$_1$ $\ldots$ {\term}$_n$ using {\qualid}} - - This syntax is used for the case {\qualid} denotes an induction principle - with complex predicates as the induction principles generated by - {\tt Function} or {\tt Functional Scheme} may be. - -\item \texttt{induction {\term} in {\occgoalset}} - - This syntax is used for selecting which occurrences of {\term} the - induction has to be carried on. The {\tt in {\atoccurrences}} clause is an - occurrence clause whose syntax and behavior is described in - Section~\ref{Occurrences clauses}. - - When an occurrence clause is given, an equation between {\term} and - the value it gets in each case of the induction is added to the - context of the subgoals corresponding to the induction cases (even - if no clause {\tt as {\namingintropattern}} is given). - -\item {\tt induction {\term$_1$} with {\bindinglist$_1$} as {\namingintropattern} {\disjconjintropattern} using {\term$_2$} with {\bindinglist$_2$} in {\occgoalset}}\\ - {\tt einduction {\term$_1$} with {\bindinglist$_1$} as {\namingintropattern} {\disjconjintropattern} using {\term$_2$} with {\bindinglist$_2$} in {\occgoalset}} - - These are the most general forms of {\tt induction} and {\tt - einduction}. It combines the effects of the {\tt with}, {\tt as}, - {\tt using}, and {\tt in} clauses. - -\item {\tt elim \term}\label{elim} - - This is a more basic induction tactic. Again, the type of the - argument {\term} must be an inductive type. Then, according to - the type of the goal, the tactic {\tt elim} chooses the appropriate - destructor and applies it as the tactic {\tt apply} - would do. For instance, if the proof context contains {\tt - n:nat} and the current goal is {\tt T} of type {\tt - Prop}, then {\tt elim n} is equivalent to {\tt apply nat\_ind with - (n:=n)}. The tactic {\tt elim} does not modify the context of - the goal, neither introduces the induction loading into the context - of hypotheses. - - More generally, {\tt elim \term} also works when the type of {\term} - is a statement with premises and whose conclusion is inductive. In - that case the tactic performs induction on the conclusion of the - type of {\term} and leaves the non-dependent premises of the type as - subgoals. In the case of dependent products, the tactic tries to - find an instance for which the elimination lemma applies and fails - otherwise. - -\item {\tt elim {\term} with {\bindinglist}} - - Allows to give explicit instances to the premises of the type - of {\term} (see Section~\ref{Binding-list}). - -\item{\tt eelim {\term}\tacindex{eelim}} - - In case the type of {\term} has dependent premises, this turns them into - existential variables to be resolved later on. - -\item{\tt elim {\term$_1$} using {\term$_2$}}\\ - {\tt elim {\term$_1$} using {\term$_2$} with {\bindinglist}\tacindex{elim \dots\ using}} - -Allows the user to give explicitly an elimination predicate -{\term$_2$} which is not the standard one for the underlying inductive -type of {\term$_1$}. The {\bindinglist} clause allows to -instantiate premises of the type of {\term$_2$}. - -\item{\tt elim {\term$_1$} with {\bindinglist$_1$} using {\term$_2$} with {\bindinglist$_2$}}\\ - {\tt eelim {\term$_1$} with {\bindinglist$_1$} using {\term$_2$} with {\bindinglist$_2$}} - - These are the most general forms of {\tt elim} and {\tt eelim}. It - combines the effects of the {\tt using} clause and of the two uses - of the {\tt with} clause. - -\item {\tt elimtype \form}\tacindex{elimtype} - - The argument {\form} must be inductively defined. {\tt elimtype I} - is equivalent to {\tt cut I. intro H{\rm\sl n}; elim H{\rm\sl n}; - clear H{\rm\sl n}}. Therefore the hypothesis {\tt H{\rm\sl n}} will - not appear in the context(s) of the subgoal(s). Conversely, if {\tt - t} is a term of (inductive) type {\tt I} and which does not occur - in the goal then {\tt elim t} is equivalent to {\tt elimtype I; 2: - exact t.} - -\item {\tt simple induction \ident}\tacindex{simple induction} - - This tactic behaves as {\tt intros until - {\ident}; elim {\tt {\ident}}} when {\ident} is a quantified - variable of the goal. - -\item {\tt simple induction {\num}} - - This tactic behaves as {\tt intros until - {\num}; elim {\tt {\ident}}} where {\ident} is the name given by - {\tt intros until {\num}} to the {\num}-th non-dependent premise of - the goal. - -%% \item {\tt simple induction {\term}}\tacindex{simple induction} - -%% If {\term} is an {\ident} corresponding to a quantified variable of -%% the goal then the tactic behaves as {\tt intros until {\ident}; elim -%% {\tt {\ident}}}. If {\term} is a {\num} then the tactic behaves as -%% {\tt intros until {\ident}; elim {\tt {\ident}}}. Otherwise, it is -%% a synonym for {\tt elim {\term}}. - -%% \Rem For simple induction on a numeral, use syntax {\tt simple -%% induction ({\num})}. - -\end{Variants} - -\subsection{\tt destruct \term -\tacindex{destruct}} -\label{destruct} - -The tactic {\tt destruct} is used to perform case analysis without -recursion. Its behavior is similar to {\tt induction} except -that no induction hypothesis is generated. It applies to any goal and -the type of {\term} must be inductively defined. There are particular cases: - -\begin{itemize} - -\item If {\term} is an identifier {\ident} denoting a quantified -variable of the conclusion of the goal, then {\tt destruct {\ident}} -behaves as {\tt intros until {\ident}; destruct {\ident}}. - -\item If {\term} is a {\num}, then {\tt destruct {\num}} behaves as -{\tt intros until {\num}} followed by {\tt destruct} applied to the -last introduced hypothesis. - -\Rem For destruction of a numeral, use syntax {\tt destruct -({\num})} (not very interesting anyway). - -\end{itemize} - -\begin{Variants} -\item{\tt destruct {\term} as {\disjconjintropattern}} - - This behaves as {\tt destruct {\term}} but uses the names in - {\intropattern} to name the variables introduced in the context. - The {\intropattern} must have the form {\tt [} $p_{11}$ \ldots - $p_{1n_1}$ {\tt |} {\ldots} {\tt |} $p_{m1}$ \ldots $p_{mn_m}$ {\tt - ]} with $m$ being the number of constructors of the type of - {\term}. Each variable introduced by {\tt destruct} in the context - of the $i^{th}$ goal gets its name from the list $p_{i1}$ \ldots - $p_{in_i}$ in order. If there are not enough names, {\tt destruct} - invents names for the remaining variables to introduce. More - generally, the $p_{ij}$ can be any disjunctive/conjunctive - introduction pattern (see Section~\ref{intros-pattern}). This - provides a concise notation for nested destruction. - -% It is recommended to use this variant of {\tt destruct} for -% robust proof scripts. - -\item{\tt destruct {\term} as {\disjconjintropattern} \_eqn} - - This behaves as {\tt destruct {\term}} but adds an equation between - {\term} and the value that {\term} takes in each of the possible - cases. The name of the equation is chosen by Coq. If - {\disjconjintropattern} is simply {\tt []}, it is automatically considered - as a disjunctive pattern of the appropriate size. - -\item{\tt destruct {\term} as {\disjconjintropattern} \_eqn: {\namingintropattern}} - - This behaves as {\tt destruct {\term} as - {\disjconjintropattern} \_eqn} but use {\namingintropattern} to - name the equation (see Section~\ref{intros-pattern}). Note that spaces - can generally be removed around {\tt \_eqn}. - -\item{\tt destruct {\term} with \bindinglist} - - This behaves like \texttt{destruct {\term}} providing explicit - instances for the dependent premises of the type of {\term} (see - syntax of bindings in Section~\ref{Binding-list}). - -\item{\tt edestruct {\term}\tacindex{edestruct}} - - This tactic behaves like \texttt{destruct {\term}} excepts that it - does not fail if the instance of a dependent premises of the type of - {\term} is not inferable. Instead, the unresolved instances are left - as existential variables to be inferred later, in the same way as - {\tt eapply} does (see Section~\ref{eapply-example}). - -\item{\tt destruct {\term$_1$} using {\term$_2$}}\\ - {\tt destruct {\term$_1$} using {\term$_2$} with {\bindinglist}} - - These are synonyms of {\tt induction {\term$_1$} using {\term$_2$}} and - {\tt induction {\term$_1$} using {\term$_2$} with {\bindinglist}}. - -\item \texttt{destruct {\term} in {\occgoalset}} - - This syntax is used for selecting which occurrences of {\term} the - case analysis has to be done on. The {\tt in {\occgoalset}} clause is an - occurrence clause whose syntax and behavior is described in - Section~\ref{Occurrences clauses}. - - When an occurrence clause is given, an equation between {\term} and - the value it gets in each case of the analysis is added to the - context of the subgoals corresponding to the cases (even - if no clause {\tt as {\namingintropattern}} is given). - -\item{\tt destruct {\term$_1$} with {\bindinglist$_1$} as {\disjconjintropattern} \_eqn: {\namingintropattern} using {\term$_2$} with {\bindinglist$_2$} in {\occgoalset}}\\ - {\tt edestruct {\term$_1$} with {\bindinglist$_1$} as {\disjconjintropattern} \_eqn: {\namingintropattern} using {\term$_2$} with {\bindinglist$_2$} in {\occgoalset}} - - These are the general forms of {\tt destruct} and {\tt edestruct}. - They combine the effects of the {\tt with}, {\tt as}, {\tt using}, - and {\tt in} clauses. - -\item{\tt case \term}\label{case}\tacindex{case} - - The tactic {\tt case} is a more basic tactic to perform case - analysis without recursion. It behaves as {\tt elim \term} but using - a case-analysis elimination principle and not a recursive one. - -\item{\tt case\_eq \term}\label{case_eq}\tacindex{case\_eq} - - The tactic {\tt case\_eq} is a variant of the {\tt case} tactic that - allow to perform case analysis on a term without completely - forgetting its original form. This is done by generating equalities - between the original form of the term and the outcomes of the case - analysis. The effect of this tactic is similar to the effect of {\tt - destruct {\term} in |- *} with the exception that no new hypotheses - are introduced in the context. - -\item {\tt case {\term} with {\bindinglist}} - - Analogous to {\tt elim {\term} with {\bindinglist}} above. - -\item{\tt ecase {\term}\tacindex{ecase}}\\ - {\tt ecase {\term} with {\bindinglist}} - - In case the type of {\term} has dependent premises, or dependent - premises whose values are not inferable from the {\tt with - {\bindinglist}} clause, {\tt ecase} turns them into existential - variables to be resolved later on. - -\item {\tt simple destruct \ident}\tacindex{simple destruct} - - This tactic behaves as {\tt intros until - {\ident}; case {\tt {\ident}}} when {\ident} is a quantified - variable of the goal. - -\item {\tt simple destruct {\num}} - - This tactic behaves as {\tt intros until - {\num}; case {\tt {\ident}}} where {\ident} is the name given by - {\tt intros until {\num}} to the {\num}-th non-dependent premise of - the goal. - - -\end{Variants} - -\subsection{\tt intros {\intropattern} {\ldots} {\intropattern} -\label{intros-pattern} -\tacindex{intros \intropattern}} -\index{Introduction patterns} -\index{Naming introduction patterns} -\index{Disjunctive/conjunctive introduction patterns} - -This extension of the tactic {\tt intros} combines introduction of -variables or hypotheses and case analysis. An {\em introduction pattern} is -either: -\begin{itemize} -\item A {\em naming introduction pattern}, i.e. either one of: - \begin{itemize} - \item the pattern \texttt{?} - \item the pattern \texttt{?\ident} - \item an identifier - \end{itemize} -\item A {\em disjunctive/conjunctive introduction pattern}, i.e. either one of: - \begin{itemize} - \item a disjunction of lists of patterns: - {\tt [$p_{11}$ {\ldots} $p_{1m_1}$ | {\ldots} | $p_{11}$ {\ldots} $p_{nm_n}$]} - \item a conjunction of patterns: {\tt (} $p_1$ {\tt ,} {\ldots} {\tt ,} $p_n$ {\tt )} - \item a list of patterns {\tt (} $p_1$\ {\tt \&}\ {\ldots}\ {\tt \&}\ $p_n$ {\tt )} - for sequence of right-associative binary constructs - \end{itemize} -\item the wildcard: {\tt \_} -\item the rewriting orientations: {\tt ->} or {\tt <-} -\end{itemize} - -Assuming a goal of type {\tt $Q$ -> $P$} (non dependent product), or -of type {\tt forall $x$:$T$, $P$} (dependent product), the behavior of -{\tt intros $p$} is defined inductively over the structure of the -introduction pattern $p$: -\begin{itemize} -\item introduction on \texttt{?} performs the introduction, and lets {\Coq} - choose a fresh name for the variable; -\item introduction on \texttt{?\ident} performs the introduction, and - lets {\Coq} choose a fresh name for the variable based on {\ident}; -\item introduction on \texttt{\ident} behaves as described in - Section~\ref{intro}; -\item introduction over a disjunction of list of patterns {\tt - [$p_{11}$ {\ldots} $p_{1m_1}$ | {\ldots} | $p_{11}$ {\ldots} - $p_{nm_n}$]} expects the product to be over an inductive type - whose number of constructors is $n$ (or more generally over a type - of conclusion an inductive type built from $n$ constructors, - e.g. {\tt C -> A$\backslash$/B if $n=2$}): it destructs the introduced - hypothesis as {\tt destruct} (see Section~\ref{destruct}) would and - applies on each generated subgoal the corresponding tactic; - \texttt{intros}~$p_{i1}$ {\ldots} $p_{im_i}$; if the disjunctive - pattern is part of a sequence of patterns and is not the last - pattern of the sequence, then {\Coq} completes the pattern so as all - the argument of the constructors of the inductive type are - introduced (for instance, the list of patterns {\tt [$\;$|$\;$] H} - applied on goal {\tt forall x:nat, x=0 -> 0=x} behaves the same as - the list of patterns {\tt [$\,$|$\,$?$\,$] H}); -\item introduction over a conjunction of patterns {\tt ($p_1$, \ldots, - $p_n$)} expects the goal to be a product over an inductive type $I$ with a - single constructor that itself has at least $n$ arguments: it - performs a case analysis over the hypothesis, as {\tt destruct} - would, and applies the patterns $p_1$~\ldots~$p_n$ to the arguments - of the constructor of $I$ (observe that {\tt ($p_1$, {\ldots}, - $p_n$)} is an alternative notation for {\tt [$p_1$ {\ldots} - $p_n$]}); -\item introduction via {\tt ( $p_1$ \& \ldots \& $p_n$ )} - is a shortcut for introduction via - {\tt ($p_1$,(\ldots,(\dots,$p_n$)\ldots))}; it expects the - hypothesis to be a sequence of right-associative binary inductive - constructors such as {\tt conj} or {\tt ex\_intro}; for instance, an - hypothesis with type {\tt A\verb|/\|exists x, B\verb|/\|C\verb|/\|D} can be - introduced via pattern {\tt (a \& x \& b \& c \& d)}; -\item introduction on the wildcard depends on whether the product is - dependent or not: in the non dependent case, it erases the - corresponding hypothesis (i.e. it behaves as an {\tt intro} followed - by a {\tt clear}, cf Section~\ref{clear}) while in the dependent - case, it succeeds and erases the variable only if the wildcard is - part of a more complex list of introduction patterns that also - erases the hypotheses depending on this variable; -\item introduction over {\tt ->} (respectively {\tt <-}) expects the - hypothesis to be an equality and the right-hand-side (respectively - the left-hand-side) is replaced by the left-hand-side (respectively - the right-hand-side) in both the conclusion and the context of the goal; - if moreover the term to substitute is a variable, the hypothesis is - removed. -\end{itemize} - -\Rem {\tt intros $p_1~\ldots~p_n$} is not equivalent to \texttt{intros - $p_1$;\ldots; intros $p_n$} for the following reasons: -\begin{itemize} -\item A wildcard pattern never succeeds when applied isolated on a - dependent product, while it succeeds as part of a list of - introduction patterns if the hypotheses that depends on it are - erased too. -\item A disjunctive or conjunctive pattern followed by an introduction - pattern forces the introduction in the context of all arguments of - the constructors before applying the next pattern while a terminal - disjunctive or conjunctive pattern does not. Here is an example - -\begin{coq_example} -Goal forall n:nat, n = 0 -> n = 0. -intros [ | ] H. -Show 2. -Undo. -intros [ | ]; intros H. -Show 2. -\end{coq_example} - -\end{itemize} - -\begin{coq_example} -Lemma intros_test : forall A B C:Prop, A \/ B /\ C -> (A -> C) -> C. -intros A B C [a| [_ c]] f. -apply (f a). -exact c. -Qed. -\end{coq_example} - -%\subsection[\tt FixPoint \dots]{\tt FixPoint \dots\tacindex{Fixpoint}} -%Not yet documented. - -\subsection{\tt double induction \ident$_1$ \ident$_2$} -%\tacindex{double induction}} -This tactic is deprecated and should be replaced by {\tt induction \ident$_1$; induction \ident$_2$} (or {\tt induction \ident$_1$; destruct \ident$_2$} depending on the exact needs). - -%% This tactic applies to any goal. If the variables {\ident$_1$} and -%% {\ident$_2$} of the goal have an inductive type, then this tactic -%% performs double induction on these variables. For instance, if the -%% current goal is \verb+forall n m:nat, P n m+ then, {\tt double induction n -%% m} yields the four cases with their respective inductive hypotheses. - -%% In particular, for proving \verb+(P (S n) (S m))+, the generated induction -%% hypotheses are \verb+(P (S n) m)+ and \verb+(m:nat)(P n m)+ (of the latter, -%% \verb+(P n m)+ and \verb+(P n (S m))+ are derivable). - -%% \Rem When the induction hypothesis \verb+(P (S n) m)+ is not -%% needed, {\tt induction \ident$_1$; destruct \ident$_2$} produces -%% more concise subgoals. - -\begin{Variant} - -\item {\tt double induction \num$_1$ \num$_2$} - -This tactic is deprecated and should be replaced by {\tt induction - \num$_1$; induction \num$_3$} where \num$_3$ is the result of -\num$_2$-\num$_1$. - -%% This tactic applies to any goal. If the variables {\ident$_1$} and - -%% This applies double induction on the \num$_1^{th}$ and \num$_2^{th}$ {\it -%% non dependent} premises of the goal. More generally, any combination of an -%% {\ident} and a {\num} is valid. - -\end{Variant} - -\subsection{\tt dependent induction \ident - \tacindex{dependent induction} - \label{DepInduction}} - -The \emph{experimental} tactic \texttt{dependent induction} performs -induction-inversion on an instantiated inductive predicate. -One needs to first require the {\tt Coq.Program.Equality} module to use -this tactic. The tactic is based on the BasicElim tactic by Conor -McBride \cite{DBLP:conf/types/McBride00} and the work of Cristina Cornes -around inversion \cite{DBLP:conf/types/CornesT95}. From an instantiated -inductive predicate and a goal it generates an equivalent goal where the -hypothesis has been generalized over its indexes which are then -constrained by equalities to be the right instances. This permits to -state lemmas without resorting to manually adding these equalities and -still get enough information in the proofs. -A simple example is the following: - -\begin{coq_eval} -Reset Initial. -\end{coq_eval} -\begin{coq_example} -Lemma le_minus : forall n:nat, n < 1 -> n = 0. -intros n H ; induction H. -\end{coq_example} - -Here we didn't get any information on the indexes to help fulfill this -proof. The problem is that when we use the \texttt{induction} tactic -we lose information on the hypothesis instance, notably that the second -argument is \texttt{1} here. Dependent induction solves this problem by -adding the corresponding equality to the context. - -\begin{coq_eval} -Reset Initial. -\end{coq_eval} -\begin{coq_example} -Require Import Coq.Program.Equality. -Lemma le_minus : forall n:nat, n < 1 -> n = 0. -intros n H ; dependent induction H. -\end{coq_example} - -The subgoal is cleaned up as the tactic tries to automatically -simplify the subgoals with respect to the generated equalities. -In this enriched context it becomes possible to solve this subgoal. -\begin{coq_example} -reflexivity. -\end{coq_example} - -Now we are in a contradictory context and the proof can be solved. -\begin{coq_example} -inversion H. -\end{coq_example} - -This technique works with any inductive predicate. -In fact, the \texttt{dependent induction} tactic is just a wrapper around -the \texttt{induction} tactic. One can make its own variant by just -writing a new tactic based on the definition found in -\texttt{Coq.Program.Equality}. Common useful variants are the following, -defined in the same file: - -\begin{Variants} -\item {\tt dependent induction {\ident} generalizing {\ident$_1$} \dots - {\ident$_n$}}\tacindex{dependent induction \dots\ generalizing} - - Does dependent induction on the hypothesis {\ident} but first - generalizes the goal by the given variables so that they are - universally quantified in the goal. This is generally what one wants - to do with the variables that are inside some constructors in the - induction hypothesis. The other ones need not be further generalized. - -\item {\tt dependent destruction {\ident}}\tacindex{dependent destruction} - - Does the generalization of the instance {\ident} but uses {\tt destruct} - instead of {\tt induction} on the generalized hypothesis. This gives - results equivalent to {\tt inversion} or {\tt dependent inversion} if - the hypothesis is dependent. -\end{Variants} - -A larger example of dependent induction and an explanation of the -underlying technique are developed in section~\ref{dependent-induction-example}. - -\subsection{\tt decompose [ {\qualid$_1$} \dots\ {\qualid$_n$} ] \term -\label{decompose} -\tacindex{decompose}} - -This tactic allows to recursively decompose a -complex proposition in order to obtain atomic ones. -Example: - -\begin{coq_eval} -Reset Initial. -\end{coq_eval} -\begin{coq_example} -Lemma ex1 : forall A B C:Prop, A /\ B /\ C \/ B /\ C \/ C /\ A -> C. -intros A B C H; decompose [and or] H; assumption. -\end{coq_example} -\begin{coq_example*} -Qed. -\end{coq_example*} - -{\tt decompose} does not work on right-hand sides of implications or products. - -\begin{Variants} - -\item {\tt decompose sum \term}\tacindex{decompose sum} - This decomposes sum types (like \texttt{or}). -\item {\tt decompose record \term}\tacindex{decompose record} - This decomposes record types (inductive types with one constructor, - like \texttt{and} and \texttt{exists} and those defined with the - \texttt{Record} macro, see Section~\ref{Record}). -\end{Variants} - - -\subsection{\tt functional induction (\qualid\ \term$_1$ \dots\ \term$_n$). -\tacindex{functional induction} -\label{FunInduction}} - -The \emph{experimental} tactic \texttt{functional induction} performs -case analysis and induction following the definition of a function. It -makes use of a principle generated by \texttt{Function} -(see Section~\ref{Function}) or \texttt{Functional Scheme} -(see Section~\ref{FunScheme}). - -\begin{coq_eval} -Reset Initial. -\end{coq_eval} -\begin{coq_example} -Functional Scheme minus_ind := Induction for minus Sort Prop. - -Lemma le_minus : forall n m:nat, (n - m <= n). -intros n m. -functional induction (minus n m); simpl; auto. -\end{coq_example} -\begin{coq_example*} -Qed. -\end{coq_example*} - -\Rem \texttt{(\qualid\ \term$_1$ \dots\ \term$_n$)} must be a correct -full application of \qualid. In particular, the rules for implicit -arguments are the same as usual. For example use \texttt{@\qualid} if -you want to write implicit arguments explicitly. - -\Rem Parenthesis over \qualid \dots \term$_n$ are mandatory. - -\Rem \texttt{functional induction (f x1 x2 x3)} is actually a wrapper -for \texttt{induction x1 x2 x3 (f x1 x2 x3) using \qualid} followed by -a cleaning phase, where $\qualid$ is the induction principle -registered for $f$ (by the \texttt{Function} (see Section~\ref{Function}) -or \texttt{Functional Scheme} (see Section~\ref{FunScheme}) command) -corresponding to the sort of the goal. Therefore \texttt{functional - induction} may fail if the induction scheme (\texttt{\qualid}) is -not defined. See also Section~\ref{Function} for the function terms -accepted by \texttt{Function}. - -\Rem There is a difference between obtaining an induction scheme for a -function by using \texttt{Function} (see Section~\ref{Function}) and by -using \texttt{Functional Scheme} after a normal definition using -\texttt{Fixpoint} or \texttt{Definition}. See \ref{Function} for -details. - -\SeeAlso{\ref{Function},\ref{FunScheme},\ref{FunScheme-examples}, - \ref{sec:functional-inversion}} - -\begin{ErrMsgs} -\item \errindex{Cannot find induction information on \qualid} - - ~ - -\item \errindex{Not the right number of induction arguments} -\end{ErrMsgs} - -\begin{Variants} -\item {\tt functional induction (\qualid\ \term$_1$ \dots\ \term$_n$) - using \term$_{m+1}$ with {\term$_{n+1}$} \dots {\term$_m$}} - - Similar to \texttt{Induction} and \texttt{elim} - (see Section~\ref{Tac-induction}), allows to give explicitly the - induction principle and the values of dependent premises of the - elimination scheme, including \emph{predicates} for mutual induction - when {\qualid} is part of a mutually recursive definition. - -\item {\tt functional induction (\qualid\ \term$_1$ \dots\ \term$_n$) - using \term$_{m+1}$ with {\vref$_1$} := {\term$_{n+1}$} \dots\ - {\vref$_m$} := {\term$_n$}} - - Similar to \texttt{induction} and \texttt{elim} - (see Section~\ref{Tac-induction}). - -\item All previous variants can be extended by the usual \texttt{as - \intropattern} construction, similar for example to - \texttt{induction} and \texttt{elim} (see Section~\ref{Tac-induction}). - -\end{Variants} - - - -\section{Equality} - -These tactics use the equality {\tt eq:forall A:Type, A->A->Prop} -defined in file {\tt Logic.v} (see Section~\ref{Equality}). The -notation for {\tt eq}~$T~t~u$ is simply {\tt $t$=$u$} dropping the -implicit type of $t$ and $u$. - -\subsection{\tt rewrite \term -\label{rewrite} -\tacindex{rewrite}} - -This tactic applies to any goal. The type of {\term} -must have the form - -\texttt{forall (x$_1$:A$_1$) \dots\ (x$_n$:A$_n$)}\texttt{eq} \term$_1$ \term$_2$. - -\noindent where \texttt{eq} is the Leibniz equality or a registered -setoid equality. - -\noindent Then {\tt rewrite \term} finds the first subterm matching -\term$_1$ in the goal, resulting in instances \term$_1'$ and \term$_2'$ -and then replaces every occurrence of \term$_1'$ by \term$_2'$. -Hence, some of the variables x$_i$ are -solved by unification, and some of the types \texttt{A}$_1$, \dots, -\texttt{A}$_n$ become new subgoals. - -% \Rem In case the type of -% \term$_1$ contains occurrences of variables bound in the -% type of \term, the tactic tries first to find a subterm of the goal -% which matches this term in order to find a closed instance \term$'_1$ -% of \term$_1$, and then all instances of \term$'_1$ will be replaced. - -\begin{ErrMsgs} -\item \errindex{The term provided does not end with an equation} - -\item \errindex{Tactic generated a subgoal identical to the original goal}\\ -This happens if \term$_1$ does not occur in the goal. -\end{ErrMsgs} - -\begin{Variants} -\item {\tt rewrite -> {\term}}\tacindex{rewrite ->}\\ - Is equivalent to {\tt rewrite \term} - -\item {\tt rewrite <- {\term}}\tacindex{rewrite <-}\\ - Uses the equality \term$_1${\tt=}\term$_2$ from right to left - -\item {\tt rewrite {\term} in \textit{clause}} - \tacindex{rewrite \dots\ in}\\ - Analogous to {\tt rewrite {\term}} but rewriting is done following - \textit{clause} (similarly to \ref{Conversion-tactics}). For - instance: - \begin{itemize} - \item \texttt{rewrite H in H1} will rewrite \texttt{H} in the hypothesis - \texttt{H1} instead of the current goal. - \item \texttt{rewrite H in H1 at 1, H2 at - 2 |- *} means \texttt{rewrite H; rewrite H in H1 at 1; - rewrite H in H2 at - 2}. In particular a failure will happen if any of - these three simpler tactics fails. - \item \texttt{rewrite H in * |- } will do \texttt{rewrite H in - H$_i$} for all hypothesis \texttt{H$_i$ <> H}. A success will happen - as soon as at least one of these simpler tactics succeeds. - \item \texttt{rewrite H in *} is a combination of \texttt{rewrite H} - and \texttt{rewrite H in * |-} that succeeds if at - least one of these two tactics succeeds. - \end{itemize} - Orientation {\tt ->} or {\tt <-} can be - inserted before the term to rewrite. - -\item {\tt rewrite {\term} at {\occlist}} - \tacindex{rewrite \dots\ at} - - Rewrite only the given occurrences of \term$_1'$. Occurrences are - specified from left to right as for \texttt{pattern} (\S - \ref{pattern}). The rewrite is always performed using setoid - rewriting, even for Leibniz's equality, so one has to - \texttt{Import Setoid} to use this variant. - -\item {\tt rewrite {\term} by {\tac}} - \tacindex{rewrite \dots\ by} - - Use {\tac} to completely solve the side-conditions arising from the - rewrite. - -\item {\tt rewrite $\term_1$, \ldots, $\term_n$}\\ - Is equivalent to the $n$ successive tactics {\tt rewrite $\term_1$} - up to {\tt rewrite $\term_n$}, each one working on the first subgoal - generated by the previous one. - Orientation {\tt ->} or {\tt <-} can be - inserted before each term to rewrite. One unique \textit{clause} - can be added at the end after the keyword {\tt in}; it will - then affect all rewrite operations. - -\item In all forms of {\tt rewrite} described above, a term to rewrite - can be immediately prefixed by one of the following modifiers: - \begin{itemize} - \item {\tt ?} : the tactic {\tt rewrite ?$\term$} performs the - rewrite of $\term$ as many times as possible (perhaps zero time). - This form never fails. - \item {\tt $n$?} : works similarly, except that it will do at most - $n$ rewrites. - \item {\tt !} : works as {\tt ?}, except that at least one rewrite - should succeed, otherwise the tactic fails. - \item {\tt $n$!} (or simply {\tt $n$}) : precisely $n$ rewrites - of $\term$ will be done, leading to failure if these $n$ rewrites are not possible. - \end{itemize} - -\item {\tt erewrite {\term}\tacindex{erewrite}} - -This tactic works as {\tt rewrite {\term}} but turning unresolved -bindings into existential variables, if any, instead of failing. It has -the same variants as {\tt rewrite} has. - -\end{Variants} - - -\subsection{\tt cutrewrite -> \term$_1$ = \term$_2$ -\label{cutrewrite} -\tacindex{cutrewrite}} - -This tactic acts like {\tt replace {\term$_1$} with {\term$_2$}} -(see below). - -\subsection{\tt replace {\term$_1$} with {\term$_2$} -\label{tactic:replace} -\tacindex{replace \dots\ with}} - -This tactic applies to any goal. It replaces all free occurrences of -{\term$_1$} in the current goal with {\term$_2$} and generates the -equality {\term$_2$}{\tt =}{\term$_1$} as a subgoal. This equality is -automatically solved if it occurs amongst the assumption, or if its -symmetric form occurs. It is equivalent to {\tt cut -\term$_2$=\term$_1$; [intro H{\sl n}; rewrite <- H{\sl n}; clear H{\sl -n}| assumption || symmetry; try assumption]}. - -\begin{ErrMsgs} -\item \errindex{terms do not have convertible types} -\end{ErrMsgs} - -\begin{Variants} -\item {\tt replace {\term$_1$} with {\term$_2$} by \tac}\\ This acts - as {\tt replace {\term$_1$} with {\term$_2$}} but applies {\tt \tac} - to solve the generated subgoal {\tt \term$_2$=\term$_1$}. -\item {\tt replace {\term}}\\ Replace {\term} with {\term'} using the - first assumption whose type has the form {\tt \term=\term'} or {\tt - \term'=\term} -\item {\tt replace -> {\term}}\\ Replace {\term} with {\term'} using the - first assumption whose type has the form {\tt \term=\term'} -\item {\tt replace <- {\term}}\\ Replace {\term} with {\term'} using the - first assumption whose type has the form {\tt \term'=\term} -\item {\tt replace {\term$_1$} with {\term$_2$} \textit{clause} }\\ - {\tt replace {\term$_1$} with {\term$_2$} \textit{clause} by \tac }\\ - {\tt replace {\term} \textit{clause}}\\ - {\tt replace -> {\term} \textit{clause}}\\ - {\tt replace <- {\term} \textit{clause}}\\ - Act as before but the replacements take place in - \textit{clause}~(see Section~\ref{Conversion-tactics}) and not only - in the conclusion of the goal.\\ - The \textit{clause} argument must not contain any \texttt{type of} nor \texttt{value of}. -\end{Variants} - -\subsection{\tt reflexivity -\label{reflexivity} -\tacindex{reflexivity}} - -This tactic applies to a goal which has the form {\tt t=u}. It checks -that {\tt t} and {\tt u} are convertible and then solves the goal. -It is equivalent to {\tt apply refl\_equal}. - -\begin{ErrMsgs} -\item \errindex{The conclusion is not a substitutive equation} -\item \errindex{Impossible to unify \dots\ with \dots.} -\end{ErrMsgs} - -\subsection{\tt symmetry -\tacindex{symmetry} -\tacindex{symmetry in}} -This tactic applies to a goal which has the form {\tt t=u} and changes it -into {\tt u=t}. - -\variant {\tt symmetry in {\ident}}\\ -If the statement of the hypothesis {\ident} has the form {\tt t=u}, -the tactic changes it to {\tt u=t}. - -\subsection{\tt transitivity \term -\tacindex{transitivity}} -This tactic applies to a goal which has the form {\tt t=u} -and transforms it into the two subgoals -{\tt t={\term}} and {\tt {\term}=u}. - -\subsection{\tt subst {\ident} -\tacindex{subst}} - -This tactic applies to a goal which has \ident\ in its context and -(at least) one hypothesis, say {\tt H}, of type {\tt - \ident=t} or {\tt t=\ident}. Then it replaces -\ident\ by {\tt t} everywhere in the goal (in the hypotheses -and in the conclusion) and clears \ident\ and {\tt H} from the context. - -\Rem -When several hypotheses have the form {\tt \ident=t} or {\tt - t=\ident}, the first one is used. - -\begin{Variants} - \item {\tt subst \ident$_1$ \dots \ident$_n$} \\ - Is equivalent to {\tt subst \ident$_1$; \dots; subst \ident$_n$}. - \item {\tt subst} \\ - Applies {\tt subst} repeatedly to all identifiers from the context - for which an equality exists. -\end{Variants} - -\subsection[{\tt stepl {\term}}]{{\tt stepl {\term}}\tacindex{stepl}} - -This tactic is for chaining rewriting steps. It assumes a goal of the -form ``$R$ {\term}$_1$ {\term}$_2$'' where $R$ is a binary relation -and relies on a database of lemmas of the form {\tt forall} $x$ $y$ -$z$, $R$ $x$ $y$ {\tt ->} $eq$ $x$ $z$ {\tt ->} $R$ $z$ $y$ where $eq$ -is typically a setoid equality. The application of {\tt stepl {\term}} -then replaces the goal by ``$R$ {\term} {\term}$_2$'' and adds a new -goal stating ``$eq$ {\term} {\term}$_1$''. - -Lemmas are added to the database using the command -\comindex{Declare Left Step} -\begin{quote} -{\tt Declare Left Step {\term}.} -\end{quote} - -The tactic is especially useful for parametric setoids which are not -accepted as regular setoids for {\tt rewrite} and {\tt - setoid\_replace} (see Chapter~\ref{setoid_replace}). - -\tacindex{stepr} -\comindex{Declare Right Step} -\begin{Variants} -\item{\tt stepl {\term} by {\tac}}\\ -This applies {\tt stepl {\term}} then applies {\tac} to the second goal. - -\item{\tt stepr {\term}}\\ - {\tt stepr {\term} by {\tac}}\\ -This behaves as {\tt stepl} but on the right-hand-side of the binary relation. -Lemmas are expected to be of the form -``{\tt forall} $x$ $y$ -$z$, $R$ $x$ $y$ {\tt ->} $eq$ $y$ $z$ {\tt ->} $R$ $x$ $z$'' -and are registered using the command -\begin{quote} -{\tt Declare Right Step {\term}.} -\end{quote} -\end{Variants} - - -\subsection{\tt f\_equal -\label{f-equal} -\tacindex{f\_equal}} - -This tactic applies to a goal of the form $f\ a_1\ \ldots\ a_n = f'\ -a'_1\ \ldots\ a'_n$. Using {\tt f\_equal} on such a goal leads to -subgoals $f=f'$ and $a_1=a'_1$ and so on up to $a_n=a'_n$. Amongst -these subgoals, the simple ones (e.g. provable by -reflexivity or congruence) are automatically solved by {\tt f\_equal}. - - -\section{Equality and inductive sets} - -We describe in this section some special purpose tactics dealing with -equality and inductive sets or types. These tactics use the equality -{\tt eq:forall (A:Type), A->A->Prop}, simply written with the -infix symbol {\tt =}. - -\subsection{\tt decide equality -\label{decideequality} -\tacindex{decide equality}} - -This tactic solves a goal of the form -{\tt forall $x$ $y$:$R$, \{$x$=$y$\}+\{\verb|~|$x$=$y$\}}, where $R$ -is an inductive type such that its constructors do not take proofs or -functions as arguments, nor objects in dependent types. - -\begin{Variants} -\item {\tt decide equality {\term}$_1$ {\term}$_2$ }.\\ - Solves a goal of the form {\tt \{}\term$_1${\tt =}\term$_2${\tt -\}+\{\verb|~|}\term$_1${\tt =}\term$_2${\tt \}}. -\end{Variants} - -\subsection{\tt compare \term$_1$ \term$_2$ -\tacindex{compare}} - -This tactic compares two given objects \term$_1$ and \term$_2$ -of an inductive datatype. If $G$ is the current goal, it leaves the sub-goals -\term$_1${\tt =}\term$_2$ {\tt ->} $G$ and \verb|~|\term$_1${\tt =}\term$_2$ -{\tt ->} $G$. The type -of \term$_1$ and \term$_2$ must satisfy the same restrictions as in the tactic -\texttt{decide equality}. - -\subsection{\tt discriminate {\term} -\label{discriminate} -\tacindex{discriminate} -\tacindex{ediscriminate}} - -This tactic proves any goal from an assumption stating that two -structurally different terms of an inductive set are equal. For -example, from {\tt (S (S O))=(S O)} we can derive by absurdity any -proposition. - -The argument {\term} is assumed to be a proof of a statement -of conclusion {\tt{\term$_1$} = {\term$_2$}} with {\term$_1$} and -{\term$_2$} being elements of an inductive set. To build the proof, -the tactic traverses the normal forms\footnote{Reminder: opaque - constants will not be expanded by $\delta$ reductions} of -{\term$_1$} and {\term$_2$} looking for a couple of subterms {\tt u} -and {\tt w} ({\tt u} subterm of the normal form of {\term$_1$} and -{\tt w} subterm of the normal form of {\term$_2$}), placed at the same -positions and whose head symbols are two different constructors. If -such a couple of subterms exists, then the proof of the current goal -is completed, otherwise the tactic fails. - -\Rem The syntax {\tt discriminate {\ident}} can be used to refer to a -hypothesis quantified in the goal. In this case, the quantified -hypothesis whose name is {\ident} is first introduced in the local -context using \texttt{intros until \ident}. - -\begin{ErrMsgs} -\item \errindex{No primitive equality found} -\item \errindex{Not a discriminable equality} -\end{ErrMsgs} - -\begin{Variants} -\item \texttt{discriminate} \num - - This does the same thing as \texttt{intros until \num} followed by - \texttt{discriminate \ident} where {\ident} is the identifier for - the last introduced hypothesis. - -\item \texttt{discriminate} {\term} {\tt with} {\bindinglist} - - This does the same thing as \texttt{discriminate {\term}} but using -the given bindings to instantiate parameters or hypotheses of {\term}. - -\item \texttt{ediscriminate} \num\\ - \texttt{ediscriminate} {\term} \zeroone{{\tt with} {\bindinglist}} - - This works the same as {\tt discriminate} but if the type of {\term}, - or the type of the hypothesis referred to by {\num}, has uninstantiated - parameters, these parameters are left as existential variables. - -\item \texttt{discriminate} - - This behaves like {\tt discriminate {\ident}} if {\ident} is the - name of an hypothesis to which {\tt discriminate} is applicable; if - the current goal is of the form {\term$_1$} {\tt <>} {\term$_2$}, - this behaves as {\tt intro {\ident}; injection {\ident}}. - - \begin{ErrMsgs} - \item \errindex{No discriminable equalities} \\ - occurs when the goal does not verify the expected preconditions. - \end{ErrMsgs} -\end{Variants} - -\subsection{\tt injection {\term} -\label{injection} -\tacindex{injection} -\tacindex{einjection}} - -The {\tt injection} tactic is based on the fact that constructors of -inductive sets are injections. That means that if $c$ is a constructor -of an inductive set, and if $(c~\vec{t_1})$ and $(c~\vec{t_2})$ are two -terms that are equal then $~\vec{t_1}$ and $~\vec{t_2}$ are equal -too. - -If {\term} is a proof of a statement of conclusion - {\tt {\term$_1$} = {\term$_2$}}, -then {\tt injection} applies injectivity as deep as possible to -derive the equality of all the subterms of {\term$_1$} and {\term$_2$} -placed in the same positions. For example, from {\tt (S - (S n))=(S (S (S m))} we may derive {\tt n=(S m)}. To use this -tactic {\term$_1$} and {\term$_2$} should be elements of an inductive -set and they should be neither explicitly equal, nor structurally -different. We mean by this that, if {\tt n$_1$} and {\tt n$_2$} are -their respective normal forms, then: -\begin{itemize} -\item {\tt n$_1$} and {\tt n$_2$} should not be syntactically equal, -\item there must not exist any pair of subterms {\tt u} and {\tt w}, - {\tt u} subterm of {\tt n$_1$} and {\tt w} subterm of {\tt n$_2$} , - placed in the same positions and having different constructors as - head symbols. -\end{itemize} -If these conditions are satisfied, then, the tactic derives the -equality of all the subterms of {\term$_1$} and {\term$_2$} placed in -the same positions and puts them as antecedents of the current goal. - -\Example Consider the following goal: - -\begin{coq_example*} -Inductive list : Set := - | nil : list - | cons : nat -> list -> list. -Variable P : list -> Prop. -\end{coq_example*} -\begin{coq_eval} -Lemma ex : - forall (l:list) (n:nat), P nil -> cons n l = cons 0 nil -> P l. -intros l n H H0. -\end{coq_eval} -\begin{coq_example} -Show. -injection H0. -\end{coq_example} -\begin{coq_eval} -Abort. -\end{coq_eval} - -Beware that \texttt{injection} yields always an equality in a sigma type -whenever the injected object has a dependent type. - -\Rem There is a special case for dependent pairs. If we have a decidable -equality over the type of the first argument, then it is safe to do -the projection on the second one, and so {\tt injection} will work fine. -To define such an equality, you have to use the {\tt Scheme} command -(see \ref{Scheme}). - -\Rem If some quantified hypothesis of the goal is named {\ident}, then -{\tt injection {\ident}} first introduces the hypothesis in the local -context using \texttt{intros until \ident}. - -\begin{ErrMsgs} -\item \errindex{Not a projectable equality but a discriminable one} -\item \errindex{Nothing to do, it is an equality between convertible terms} -\item \errindex{Not a primitive equality} -\end{ErrMsgs} - -\begin{Variants} -\item \texttt{injection} \num{} - - This does the same thing as \texttt{intros until \num} followed by -\texttt{injection \ident} where {\ident} is the identifier for the last -introduced hypothesis. - -\item \texttt{injection} \term{} {\tt with} {\bindinglist} - - This does the same as \texttt{injection {\term}} but using - the given bindings to instantiate parameters or hypotheses of {\term}. - -\item \texttt{einjection} \num\\ - \texttt{einjection} \term{} \zeroone{{\tt with} {\bindinglist}} - - This works the same as {\tt injection} but if the type of {\term}, - or the type of the hypothesis referred to by {\num}, has uninstantiated - parameters, these parameters are left as existential variables. - -\item{\tt injection} - - If the current goal is of the form {\term$_1$} {\tt <>} {\term$_2$}, - this behaves as {\tt intro {\ident}; injection {\ident}}. - - \ErrMsg \errindex{goal does not satisfy the expected preconditions} - -\item \texttt{injection} \term{} \zeroone{{\tt with} {\bindinglist}} \texttt{as} \nelist{\intropattern}{}\\ -\texttt{injection} \num{} \texttt{as} {\intropattern} {\ldots} {\intropattern}\\ -\texttt{injection} \texttt{as} {\intropattern} {\ldots} {\intropattern}\\ -\texttt{einjection} \term{} \zeroone{{\tt with} {\bindinglist}} \texttt{as} \nelist{\intropattern}{}\\ -\texttt{einjection} \num{} \texttt{as} {\intropattern} {\ldots} {\intropattern}\\ -\texttt{einjection} \texttt{as} {\intropattern} {\ldots} {\intropattern}\\ -\tacindex{injection \ldots{} as} - -These variants apply \texttt{intros} \nelist{\intropattern}{} after -the call to \texttt{injection} or \texttt{einjection}. - -\end{Variants} - -\subsection{\tt simplify\_eq {\term} -\tacindex{simplify\_eq} -\tacindex{esimplify\_eq} -\label{simplify-eq}} - -Let {\term} be the proof of a statement of conclusion {\tt - {\term$_1$}={\term$_2$}}. If {\term$_1$} and -{\term$_2$} are structurally different (in the sense described for the -tactic {\tt discriminate}), then the tactic {\tt simplify\_eq} behaves as {\tt - discriminate {\term}}, otherwise it behaves as {\tt injection - {\term}}. - -\Rem If some quantified hypothesis of the goal is named {\ident}, then -{\tt simplify\_eq {\ident}} first introduces the hypothesis in the local -context using \texttt{intros until \ident}. - -\begin{Variants} -\item \texttt{simplify\_eq} \num - - This does the same thing as \texttt{intros until \num} then -\texttt{simplify\_eq \ident} where {\ident} is the identifier for the last -introduced hypothesis. - -\item \texttt{simplify\_eq} \term{} {\tt with} {\bindinglist} - - This does the same as \texttt{simplify\_eq {\term}} but using - the given bindings to instantiate parameters or hypotheses of {\term}. - -\item \texttt{esimplify\_eq} \num\\ - \texttt{esimplify\_eq} \term{} \zeroone{{\tt with} {\bindinglist}} - - This works the same as {\tt simplify\_eq} but if the type of {\term}, - or the type of the hypothesis referred to by {\num}, has uninstantiated - parameters, these parameters are left as existential variables. - -\item{\tt simplify\_eq} - -If the current goal has form $t_1\verb=<>=t_2$, it behaves as -\texttt{intro {\ident}; simplify\_eq {\ident}}. -\end{Variants} - -\subsection{\tt dependent rewrite -> {\ident} -\tacindex{dependent rewrite ->} -\label{dependent-rewrite}} - -This tactic applies to any goal. If \ident\ has type -\verb+(existT B a b)=(existT B a' b')+ -in the local context (i.e. each term of the -equality has a sigma type $\{ a:A~ \&~(B~a)\}$) this tactic rewrites -\verb+a+ into \verb+a'+ and \verb+b+ into \verb+b'+ in the current -goal. This tactic works even if $B$ is also a sigma type. This kind -of equalities between dependent pairs may be derived by the injection -and inversion tactics. - -\begin{Variants} -\item{\tt dependent rewrite <- {\ident}} -\tacindex{dependent rewrite <-} \\ -Analogous to {\tt dependent rewrite ->} but uses the equality from -right to left. -\end{Variants} - -\section{Inversion -\label{inversion}} - -\subsection{\tt inversion {\ident} -\tacindex{inversion}} - -Let the type of \ident~ in the local context be $(I~\vec{t})$, -where $I$ is a (co)inductive predicate. Then, -\texttt{inversion} applied to \ident~ derives for each possible -constructor $c_i$ of $(I~\vec{t})$, {\bf all} the necessary -conditions that should hold for the instance $(I~\vec{t})$ to be -proved by $c_i$. - -\Rem If {\ident} does not denote a hypothesis in the local context -but refers to a hypothesis quantified in the goal, then the -latter is first introduced in the local context using -\texttt{intros until \ident}. - -\begin{Variants} -\item \texttt{inversion} \num - - This does the same thing as \texttt{intros until \num} then - \texttt{inversion \ident} where {\ident} is the identifier for the - last introduced hypothesis. - -\item \tacindex{inversion\_clear} \texttt{inversion\_clear} \ident - - This behaves as \texttt{inversion} and then erases \ident~ from the - context. - -\item \tacindex{inversion \dots\ as} \texttt{inversion} {\ident} \texttt{as} {\intropattern} - - This behaves as \texttt{inversion} but using names in - {\intropattern} for naming hypotheses. The {\intropattern} must have - the form {\tt [} $p_{11}$ \ldots $p_{1n_1}$ {\tt |} {\ldots} {\tt |} - $p_{m1}$ \ldots $p_{mn_m}$ {\tt ]} with $m$ being the number of - constructors of the type of {\ident}. Be careful that the list must - be of length $m$ even if {\tt inversion} discards some cases (which - is precisely one of its roles): for the discarded cases, just use an - empty list (i.e. $n_i=0$). - - The arguments of the $i^{th}$ constructor and the - equalities that {\tt inversion} introduces in the context of the - goal corresponding to the $i^{th}$ constructor, if it exists, get - their names from the list $p_{i1}$ \ldots $p_{in_i}$ in order. If - there are not enough names, {\tt induction} invents names for the - remaining variables to introduce. In case an equation splits into - several equations (because {\tt inversion} applies {\tt injection} - on the equalities it generates), the corresponding name $p_{ij}$ in - the list must be replaced by a sublist of the form {\tt [$p_{ij1}$ - \ldots $p_{ijq}$]} (or, equivalently, {\tt ($p_{ij1}$, - \ldots, $p_{ijq}$)}) where $q$ is the number of subequalities - obtained from splitting the original equation. Here is an example. - -\begin{coq_eval} -Require Import List. -\end{coq_eval} - -\begin{coq_example} -Inductive contains0 : list nat -> Prop := - | in_hd : forall l, contains0 (0 :: l) - | in_tl : forall l b, contains0 l -> contains0 (b :: l). -Goal forall l:list nat, contains0 (1 :: l) -> contains0 l. -intros l H; inversion H as [ | l' p Hl' [Heqp Heql'] ]. -\end{coq_example} - -\begin{coq_eval} -Abort. -\end{coq_eval} - -\item \texttt{inversion} {\num} {\tt as} {\intropattern} - - This allows to name the hypotheses introduced by - \texttt{inversion} {\num} in the context. - -\item \tacindex{inversion\_cleardots\ as} \texttt{inversion\_clear} - {\ident} {\tt as} {\intropattern} - - This allows to name the hypotheses introduced by - \texttt{inversion\_clear} in the context. - -\item \tacindex{inversion \dots\ in} \texttt{inversion } {\ident} - \texttt{in} \ident$_1$ \dots\ \ident$_n$ - - Let \ident$_1$ \dots\ \ident$_n$, be identifiers in the local context. This - tactic behaves as generalizing \ident$_1$ \dots\ \ident$_n$, and - then performing \texttt{inversion}. - -\item \tacindex{inversion \dots\ as \dots\ in} \texttt{inversion } - {\ident} {\tt as} {\intropattern} \texttt{in} \ident$_1$ \dots\ - \ident$_n$ - - This allows to name the hypotheses introduced in the context by - \texttt{inversion} {\ident} \texttt{in} \ident$_1$ \dots\ - \ident$_n$. - -\item \tacindex{inversion\_clear \dots\ in} \texttt{inversion\_clear} - {\ident} \texttt{in} \ident$_1$ \ldots \ident$_n$ - - Let \ident$_1$ \dots\ \ident$_n$, be identifiers in the local context. This - tactic behaves as generalizing \ident$_1$ \dots\ \ident$_n$, and - then performing {\tt inversion\_clear}. - -\item \tacindex{inversion\_clear \dots\ as \dots\ in} - \texttt{inversion\_clear} {\ident} \texttt{as} {\intropattern} - \texttt{in} \ident$_1$ \ldots \ident$_n$ - - This allows to name the hypotheses introduced in the context by - \texttt{inversion\_clear} {\ident} \texttt{in} \ident$_1$ \ldots - \ident$_n$. - -\item \tacindex{dependent inversion} \texttt{dependent inversion} - {\ident} - - That must be used when \ident\ appears in the current goal. It acts - like \texttt{inversion} and then substitutes \ident\ for the - corresponding term in the goal. - -\item \tacindex{dependent inversion \dots\ as } \texttt{dependent - inversion} {\ident} \texttt{as} {\intropattern} - - This allows to name the hypotheses introduced in the context by - \texttt{dependent inversion} {\ident}. - -\item \tacindex{dependent inversion\_clear} \texttt{dependent - inversion\_clear} {\ident} - - Like \texttt{dependent inversion}, except that {\ident} is cleared - from the local context. - -\item \tacindex{dependent inversion\_clear \dots\ as} - \texttt{dependent inversion\_clear} {\ident}\texttt{as} {\intropattern} - - This allows to name the hypotheses introduced in the context by - \texttt{dependent inversion\_clear} {\ident}. - -\item \tacindex{dependent inversion \dots\ with} \texttt{dependent - inversion } {\ident} \texttt{ with } \term - - This variant allows you to specify the generalization of the goal. It - is useful when the system fails to generalize the goal automatically. If - {\ident} has type $(I~\vec{t})$ and $I$ has type - $forall (\vec{x}:\vec{T}), s$, then \term~ must be of type - $I:forall (\vec{x}:\vec{T}), I~\vec{x}\to s'$ where $s'$ is the - type of the goal. - -\item \tacindex{dependent inversion \dots\ as \dots\ with} - \texttt{dependent inversion } {\ident} \texttt{as} {\intropattern} - \texttt{ with } \term - - This allows to name the hypotheses introduced in the context by - \texttt{dependent inversion } {\ident} \texttt{ with } \term. - -\item \tacindex{dependent inversion\_clear \dots\ with} - \texttt{dependent inversion\_clear } {\ident} \texttt{ with } \term - - Like \texttt{dependent inversion \dots\ with} but clears {\ident} from - the local context. - -\item \tacindex{dependent inversion\_clear \dots\ as \dots\ with} - \texttt{dependent inversion\_clear } {\ident} \texttt{as} - {\intropattern} \texttt{ with } \term - - This allows to name the hypotheses introduced in the context by - \texttt{dependent inversion\_clear } {\ident} \texttt{ with } \term. - -\item \tacindex{simple inversion} \texttt{simple inversion} {\ident} - - It is a very primitive inversion tactic that derives all the necessary - equalities but it does not simplify the constraints as - \texttt{inversion} does. - -\item \tacindex{simple inversion \dots\ as} \texttt{simple inversion} - {\ident} \texttt{as} {\intropattern} - - This allows to name the hypotheses introduced in the context by - \texttt{simple inversion}. - -\item \tacindex{inversion \dots\ using} \texttt{inversion} \ident - \texttt{ using} \ident$'$ - - Let {\ident} have type $(I~\vec{t})$ ($I$ an inductive - predicate) in the local context, and \ident$'$ be a (dependent) inversion - lemma. Then, this tactic refines the current goal with the specified - lemma. - -\item \tacindex{inversion \dots\ using \dots\ in} \texttt{inversion} - {\ident} \texttt{using} \ident$'$ \texttt{in} \ident$_1$\dots\ \ident$_n$ - - This tactic behaves as generalizing \ident$_1$\dots\ \ident$_n$, - then doing \texttt{inversion} {\ident} \texttt{using} \ident$'$. - -\end{Variants} - -\SeeAlso~\ref{inversion-examples} for detailed examples - -\subsection{\tt Derive Inversion {\ident} with - ${\tt forall (}\vec{x}{\tt :}\vec{T}{\tt),} I~\vec{t}$ Sort \sort -\label{Derive-Inversion} -\comindex{Derive Inversion}} - -This command generates an inversion principle for the -\texttt{inversion \dots\ using} tactic. -Let $I$ be an inductive predicate and $\vec{x}$ the variables -occurring in $\vec{t}$. This command generates and stocks the -inversion lemma for the sort \sort~ corresponding to the instance -$forall (\vec{x}:\vec{T}), I~\vec{t}$ with the name {\ident} in the {\bf -global} environment. When applied it is equivalent to have inverted -the instance with the tactic {\tt inversion}. - -\begin{Variants} -\item \texttt{Derive Inversion\_clear} {\ident} \texttt{with} - \comindex{Derive Inversion\_clear} - $forall (\vec{x}:\vec{T}), I~\vec{t}$ \texttt{Sort} \sort~ \\ - \index{Derive Inversion\_clear \dots\ with} - When applied it is equivalent to having - inverted the instance with the tactic \texttt{inversion} - replaced by the tactic \texttt{inversion\_clear}. -\item \texttt{Derive Dependent Inversion} {\ident} \texttt{with} - $forall (\vec{x}:\vec{T}), I~\vec{t}$ \texttt{Sort} \sort~\\ - \comindex{Derive Dependent Inversion} - When applied it is equivalent to having - inverted the instance with the tactic \texttt{dependent inversion}. -\item \texttt{Derive Dependent Inversion\_clear} {\ident} \texttt{with} - $forall (\vec{x}:\vec{T}), I~\vec{t}$ \texttt{Sort} \sort~\\ - \comindex{Derive Dependent Inversion\_clear} - When applied it is equivalent to having - inverted the instance with the tactic \texttt{dependent inversion\_clear}. -\end{Variants} - -\SeeAlso \ref{inversion-examples} for examples - - - -\subsection[\tt functional inversion \ident]{\tt functional inversion \ident\label{sec:functional-inversion}} - -\texttt{functional inversion} is a \emph{highly} experimental tactic -which performs inversion on hypothesis \ident\ of the form -\texttt{\qualid\ \term$_1$\dots\term$_n$\ = \term} or \texttt{\term\ = - \qualid\ \term$_1$\dots\term$_n$} where \qualid\ must have been -defined using \texttt{Function} (see Section~\ref{Function}). - -\begin{ErrMsgs} -\item \errindex{Hypothesis {\ident} must contain at least one Function} -\item \errindex{Cannot find inversion information for hypothesis \ident} - This error may be raised when some inversion lemma failed to be - generated by Function. -\end{ErrMsgs} - -\begin{Variants} -\item {\tt functional inversion \num} - - This does the same thing as \texttt{intros until \num} then - \texttt{functional inversion \ident} where {\ident} is the - identifier for the last introduced hypothesis. -\item {\tt functional inversion \ident\ \qualid}\\ - {\tt functional inversion \num\ \qualid} - - In case the hypothesis {\ident} (or {\num}) has a type of the form - \texttt{\qualid$_1$\ \term$_1$\dots\term$_n$\ =\ \qualid$_2$\ - \term$_{n+1}$\dots\term$_{n+m}$} where \qualid$_1$ and \qualid$_2$ - are valid candidates to functional inversion, this variant allows to - choose which must be inverted. -\end{Variants} - - - -\subsection{\tt quote \ident -\tacindex{quote} -\index{2-level approach}} - -This kind of inversion has nothing to do with the tactic -\texttt{inversion} above. This tactic does \texttt{change (\ident\ - t)}, where \texttt{t} is a term built in order to ensure the -convertibility. In other words, it does inversion of the function -\ident. This function must be a fixpoint on a simple recursive -datatype: see~\ref{quote-examples} for the full details. - -\begin{ErrMsgs} -\item \errindex{quote: not a simple fixpoint}\\ - Happens when \texttt{quote} is not able to perform inversion properly. -\end{ErrMsgs} - -\begin{Variants} -\item \texttt{quote {\ident} [ \ident$_1$ \dots \ident$_n$ ]}\\ - All terms that are built only with \ident$_1$ \dots \ident$_n$ will be - considered by \texttt{quote} as constants rather than variables. -\end{Variants} - -% En attente d'un moyen de valoriser les fichiers de demos -% \SeeAlso file \texttt{theories/DEMOS/DemoQuote.v} in the distribution - -\section[Classical tactics]{Classical tactics\label{ClassicalTactics}} - -In order to ease the proving process, when the {\tt Classical} module is loaded. A few more tactics are available. Make sure to load the module using the \texttt{Require Import} command. - -\subsection{{\tt classical\_left, classical\_right} \tacindex{classical\_left} \tacindex{classical\_right}} - -The tactics \texttt{classical\_left} and \texttt{classical\_right} are the analog of the \texttt{left} and \texttt{right} but using classical logic. They can only be used for disjunctions. -Use \texttt{classical\_left} to prove the left part of the disjunction with the assumption that the negation of right part holds. -Use \texttt{classical\_right} to prove the right part of the disjunction with the assumption that the negation of left part holds. - -\section{Automatizing -\label{Automatizing}} - -\subsection{\tt auto -\label{auto} -\tacindex{auto}} - -This tactic implements a Prolog-like resolution procedure to solve the -current goal. It first tries to solve the goal using the {\tt - assumption} tactic, then it reduces the goal to an atomic one using -{\tt intros} and introducing the newly generated hypotheses as hints. -Then it looks at the list of tactics associated to the head symbol of -the goal and tries to apply one of them (starting from the tactics -with lower cost). This process is recursively applied to the generated -subgoals. - -By default, \texttt{auto} only uses the hypotheses of the current goal and the -hints of the database named {\tt core}. - -\begin{Variants} - -\item {\tt auto \num} - - Forces the search depth to be \num. The maximal search depth is 5 by - default. - -\item {\tt auto with \ident$_1$ \dots\ \ident$_n$} - - Uses the hint databases $\ident_1$ \dots\ $\ident_n$ in addition to - the database {\tt core}. See Section~\ref{Hints-databases} for the - list of pre-defined databases and the way to create or extend a - database. This option can be combined with the previous one. - -\item {\tt auto with *} - - Uses all existing hint databases, minus the special database - {\tt v62}. See Section~\ref{Hints-databases} - -\item \texttt{auto using \nterm{lemma}$_1$ , \ldots , \nterm{lemma}$_n$} - - Uses \nterm{lemma}$_1$, \ldots, \nterm{lemma}$_n$ in addition to - hints (can be combined with the \texttt{with \ident} option). If - $lemma_i$ is an inductive type, it is the collection of its - constructors which is added as hints. - -\item \texttt{auto using \nterm{lemma}$_1$ , \ldots , \nterm{lemma}$_n$ with \ident$_1$ \dots\ \ident$_n$} - - This combines the effects of the {\tt using} and {\tt with} options. - -\item {\tt trivial}\tacindex{trivial} - - This tactic is a restriction of {\tt auto} that is not recursive and - tries only hints which cost 0. Typically it solves trivial - equalities like $X=X$. - -\item \texttt{trivial with \ident$_1$ \dots\ \ident$_n$} - -\item \texttt{trivial with *} - -\end{Variants} - -\Rem {\tt auto} either solves completely the goal or else leaves it -intact. \texttt{auto} and \texttt{trivial} never fail. - -\SeeAlso Section~\ref{Hints-databases} - -\subsection{\tt eauto -\tacindex{eauto} -\label{eauto}} - -This tactic generalizes {\tt auto}. In contrast with -the latter, {\tt eauto} uses unification of the goal -against the hints rather than pattern-matching -(in other words, it uses {\tt eapply} instead of -{\tt apply}). -As a consequence, {\tt eauto} can solve such a goal: - -\begin{coq_example} -Hint Resolve ex_intro. -Goal forall P:nat -> Prop, P 0 -> exists n, P n. -eauto. -\end{coq_example} -\begin{coq_eval} -Abort. -\end{coq_eval} - -Note that {\tt ex\_intro} should be declared as an -hint. - -\SeeAlso Section~\ref{Hints-databases} - -\subsection{\tt autounfold with \ident$_1$ \dots\ \ident$_n$ -\tacindex{autounfold} -\label{autounfold}} - -This tactic unfolds constants that were declared through a {\tt Hint - Unfold} in the given databases. - -\begin{Variants} -\item {\tt autounfold with \ident$_1$ \dots\ \ident$_n$ in \textit{clause}} - - Perform the unfolding in the given clause. - -\item {\tt autounfold with *} - - Uses the unfold hints declared in all the hint databases. -\end{Variants} - - -% EXISTE ENCORE ? -% -% \subsection{\tt Prolog [ \term$_1$ \dots\ \term$_n$ ] \num} -% \tacindex{Prolog}\label{Prolog} -% This tactic, implemented by Chet Murthy, is based upon the concept of -% existential variables of Gilles Dowek, stating that resolution is a -% kind of unification. It tries to solve the current goal using the {\tt -% Assumption} tactic, the {\tt intro} tactic, and applying hypotheses -% of the local context and terms of the given list {\tt [ \term$_1$ -% \dots\ \term$_n$\ ]}. It is more powerful than {\tt auto} since it -% may apply to any theorem, even those of the form {\tt (x:A)(P x) -> Q} -% where {\tt x} does not appear free in {\tt Q}. The maximal search -% depth is {\tt \num}. - -% \begin{ErrMsgs} -% \item \errindex{Prolog failed}\\ -% The Prolog tactic was not able to prove the subgoal. -% \end{ErrMsgs} - -\subsection{\tt tauto -\tacindex{tauto} -\label{tauto}} - -This tactic implements a decision procedure for intuitionistic propositional -calculus based on the contraction-free sequent calculi LJT* of Roy Dyckhoff -\cite{Dyc92}. Note that {\tt tauto} succeeds on any instance of an -intuitionistic tautological proposition. {\tt tauto} unfolds negations -and logical equivalence but does not unfold any other definition. - -The following goal can be proved by {\tt tauto} whereas {\tt auto} -would fail: - -\begin{coq_example} -Goal forall (x:nat) (P:nat -> Prop), x = 0 \/ P x -> x <> 0 -> P x. - intros. - tauto. -\end{coq_example} -\begin{coq_eval} -Abort. -\end{coq_eval} - -Moreover, if it has nothing else to do, {\tt tauto} performs -introductions. Therefore, the use of {\tt intros} in the previous -proof is unnecessary. {\tt tauto} can for instance prove the -following: -\begin{coq_example} -(* auto would fail *) -Goal forall (A:Prop) (P:nat -> Prop), - A \/ (forall x:nat, ~ A -> P x) -> forall x:nat, ~ A -> P x. - - tauto. -\end{coq_example} -\begin{coq_eval} -Abort. -\end{coq_eval} - -\Rem In contrast, {\tt tauto} cannot solve the following goal - -\begin{coq_example*} -Goal forall (A:Prop) (P:nat -> Prop), - A \/ (forall x:nat, ~ A -> P x) -> forall x:nat, ~ ~ (A \/ P x). -\end{coq_example*} -\begin{coq_eval} -Abort. -\end{coq_eval} - -because \verb=(forall x:nat, ~ A -> P x)= cannot be treated as atomic and an -instantiation of \verb=x= is necessary. - -\subsection{\tt intuition {\tac} -\tacindex{intuition} -\label{intuition}} - -The tactic \texttt{intuition} takes advantage of the search-tree built -by the decision procedure involved in the tactic {\tt tauto}. It uses -this information to generate a set of subgoals equivalent to the -original one (but simpler than it) and applies the tactic -{\tac} to them \cite{Mun94}. If this tactic fails on some goals then -{\tt intuition} fails. In fact, {\tt tauto} is simply {\tt intuition - fail}. - -For instance, the tactic {\tt intuition auto} applied to the goal -\begin{verbatim} -(forall (x:nat), P x)/\B -> (forall (y:nat),P y)/\ P O \/B/\ P O -\end{verbatim} -internally replaces it by the equivalent one: -\begin{verbatim} -(forall (x:nat), P x), B |- P O -\end{verbatim} -and then uses {\tt auto} which completes the proof. - -Originally due to C{\'e}sar~Mu{\~n}oz, these tactics ({\tt tauto} and {\tt intuition}) -have been completely re-engineered by David~Delahaye using mainly the tactic -language (see Chapter~\ref{TacticLanguage}). The code is now much shorter and -a significant increase in performance has been noticed. The general behavior -with respect to dependent types, unfolding and introductions has -slightly changed to get clearer semantics. This may lead to some -incompatibilities. - -\begin{Variants} -\item {\tt intuition}\\ - Is equivalent to {\tt intuition auto with *}. -\end{Variants} - -% En attente d'un moyen de valoriser les fichiers de demos -%\SeeAlso file \texttt{contrib/Rocq/DEMOS/Demo\_tauto.v} - - -\subsection{\tt rtauto -\tacindex{rtauto} -\label{rtauto}} - -The {\tt rtauto} tactic solves propositional tautologies similarly to what {\tt tauto} does. The main difference is that the proof term is built using a reflection scheme applied to a sequent calculus proof of the goal. The search procedure is also implemented using a different technique. - -Users should be aware that this difference may result in faster proof-search but slower proof-checking, and {\tt rtauto} might not solve goals that {\tt tauto} would be able to solve (e.g. goals involving universal quantifiers). - -\subsection{{\tt firstorder} -\tacindex{firstorder} -\label{firstorder}} - -The tactic \texttt{firstorder} is an {\it experimental} extension of -\texttt{tauto} to -first-order reasoning, written by Pierre Corbineau. -It is not restricted to usual logical connectives but -instead may reason about any first-order class inductive definition. - -\begin{Variants} - \item {\tt firstorder {\tac}} - \tacindex{firstorder {\tac}} - - Tries to solve the goal with {\tac} when no logical rule may apply. - - \item {\tt firstorder with \ident$_1$ \dots\ \ident$_n$ } - \tacindex{firstorder with} - - Adds lemmas \ident$_1$ \dots\ \ident$_n$ to the proof-search - environment. - - \item {\tt firstorder using {\qualid}$_1$ , \dots\ , {\qualid}$_n$ } - \tacindex{firstorder using} - - Adds lemmas in {\tt auto} hints bases {\qualid}$_1$ \dots\ {\qualid}$_n$ - to the proof-search environment. If {\qualid}$_i$ refers to an inductive - type, it is the collection of its constructors which is added as hints. - -\item \texttt{firstorder using {\qualid}$_1$ , \dots\ , {\qualid}$_n$ with \ident$_1$ \dots\ \ident$_n$} - - This combines the effects of the {\tt using} and {\tt with} options. - -\end{Variants} - -Proof-search is bounded by a depth parameter which can be set by typing the -{\nobreak \tt Set Firstorder Depth $n$} \comindex{Set Firstorder Depth} -vernacular command. - -%% \subsection{{\tt jp} {\em (Jprover)} -%% \tacindex{jp} -%% \label{jprover}} - -%% The tactic \texttt{jp}, due to Huang Guan-Shieng, is an experimental -%% port of the {\em Jprover}\cite{SLKN01} semi-decision procedure for -%% first-order intuitionistic logic implemented in {\em -%% NuPRL}\cite{Kre02}. - -%% The tactic \texttt{jp}, due to Huang Guan-Shieng, is an {\it -%% experimental} port of the {\em Jprover}\cite{SLKN01} semi-decision -%% procedure for first-order intuitionistic logic implemented in {\em -%% NuPRL}\cite{Kre02}. - -%% Search may optionnaly be bounded by a multiplicity parameter -%% indicating how many (at most) copies of a formula may be used in -%% the proof process, its absence may lead to non-termination of the tactic. - -%% %\begin{coq_eval} -%% %Variable S:Set. -%% %Variables P Q:S->Prop. -%% %Variable f:S->S. -%% %\end{coq_eval} - -%% %\begin{coq_example*} -%% %Lemma example: (exists x |P x\/Q x)->(exists x |P x)\/(exists x |Q x). -%% %jp. -%% %Qed. - -%% %Lemma example2: (forall x ,P x->P (f x))->forall x,P x->P (f(f x)). -%% %jp. -%% %Qed. -%% %\end{coq_example*} - -%% \begin{Variants} -%% \item {\tt jp $n$}\\ -%% \tacindex{jp $n$} -%% Tries the {\em Jprover} procedure with multiplicities up to $n$, -%% starting from 1. -%% \item {\tt jp}\\ -%% Tries the {\em Jprover} procedure without multiplicity bound, -%% possibly running forever. -%% \end{Variants} - -%% \begin{ErrMsgs} -%% \item \errindex{multiplicity limit reached}\\ -%% The procedure tried all multiplicities below the limit and -%% failed. Goal might be solved by increasing the multiplicity limit. -%% \item \errindex{formula is not provable}\\ -%% The procedure determined that goal was not provable in -%% intuitionistic first-order logic, no matter how big the -%% multiplicity is. -%% \end{ErrMsgs} - - -% \subsection[\tt Linear]{\tt Linear\tacindex{Linear}\label{Linear}} -% The tactic \texttt{Linear}, due to Jean-Christophe Filli{\^a}atre -% \cite{Fil94}, implements a decision procedure for {\em Direct -% Predicate Calculus}, that is first-order Gentzen's Sequent Calculus -% without contraction rules \cite{KeWe84,BeKe92}. Intuitively, a -% first-order goal is provable in Direct Predicate Calculus if it can be -% proved using each hypothesis at most once. - -% Unlike the previous tactics, the \texttt{Linear} tactic does not belong -% to the initial state of the system, and it must be loaded explicitly -% with the command - -% \begin{coq_example*} -% Require Linear. -% \end{coq_example*} - -% For instance, assuming that \texttt{even} and \texttt{odd} are two -% predicates on natural numbers, and \texttt{a} of type \texttt{nat}, the -% tactic \texttt{Linear} solves the following goal - -% \begin{coq_eval} -% Variables even,odd : nat -> Prop. -% Variable a:nat. -% \end{coq_eval} - -% \begin{coq_example*} -% Lemma example : (even a) -% -> ((x:nat)((even x)->(odd (S x)))) -% -> (EX y | (odd y)). -% \end{coq_example*} - -% You can find examples of the use of \texttt{Linear} in -% \texttt{theories/DEMOS/DemoLinear.v}. -% \begin{coq_eval} -% Abort. -% \end{coq_eval} - -% \begin{Variants} -% \item {\tt Linear with \ident$_1$ \dots\ \ident$_n$}\\ -% \tacindex{Linear with} -% Is equivalent to apply first {\tt generalize \ident$_1$ \dots -% \ident$_n$} (see Section~\ref{generalize}) then the \texttt{Linear} -% tactic. So one can use axioms, lemmas or hypotheses of the local -% context with \texttt{Linear} in this way. -% \end{Variants} - -% \begin{ErrMsgs} -% \item \errindex{Not provable in Direct Predicate Calculus} -% \item \errindex{Found $n$ classical proof(s) but no intuitionistic one}\\ -% The decision procedure looks actually for classical proofs of the -% goals, and then checks that they are intuitionistic. In that case, -% classical proofs have been found, which do not correspond to -% intuitionistic ones. -% \end{ErrMsgs} - -\subsection{\tt congruence -\tacindex{congruence} -\label{congruence}} - -The tactic {\tt congruence}, by Pierre Corbineau, implements the standard Nelson and Oppen -congruence closure algorithm, which is a decision procedure for ground -equalities with uninterpreted symbols. It also include the constructor theory -(see \ref{injection} and \ref{discriminate}). -If the goal is a non-quantified equality, {\tt congruence} tries to -prove it with non-quantified equalities in the context. Otherwise it -tries to infer a discriminable equality from those in the context. Alternatively, congruence tries to prove that a hypothesis is equal to the goal or to the negation of another hypothesis. - -{\tt congruence} is also able to take advantage of hypotheses stating quantified equalities, you have to provide a bound for the number of extra equalities generated that way. Please note that one of the members of the equality must contain all the quantified variables in order for {\tt congruence} to match against it. - -\begin{coq_eval} -Reset Initial. -Variable A:Set. -Variables a b:A. -Variable f:A->A. -Variable g:A->A->A. -\end{coq_eval} - -\begin{coq_example} -Theorem T: - a=(f a) -> (g b (f a))=(f (f a)) -> (g a b)=(f (g b a)) -> (g a b)=a. -intros. -congruence. -\end{coq_example} - -\begin{coq_eval} -Reset Initial. -Variable A:Set. -Variables a c d:A. -Variable f:A->A*A. -\end{coq_eval} - -\begin{coq_example} -Theorem inj : f = pair a -> Some (f c) = Some (f d) -> c=d. -intros. -congruence. -\end{coq_example} - -\begin{Variants} - \item {\tt congruence {\sl n}}\\ - Tries to add at most {\tt \sl n} instances of hypotheses stating quantified equalities to the problem in order to solve it. A bigger value of {\tt \sl n} does not make success slower, only failure. You might consider adding some lemmas as hypotheses using {\tt assert} in order for congruence to use them. - -\end{Variants} - -\begin{Variants} -\item {\tt congruence with \term$_1$ \dots\ \term$_n$}\\ - Adds {\tt \term$_1$ \dots\ \term$_n$} to the pool of terms used by - {\tt congruence}. This helps in case you have partially applied - constructors in your goal. -\end{Variants} - -\begin{ErrMsgs} - \item \errindex{I don't know how to handle dependent equality} \\ - The decision procedure managed to find a proof of the goal or of - a discriminable equality but this proof couldn't be built in {\Coq} - because of dependently-typed functions. - \item \errindex{I couldn't solve goal} \\ - The decision procedure didn't find any way to solve the goal. - \item \errindex{Goal is solvable by congruence but some arguments are missing. Try "congruence with \dots", replacing metavariables by arbitrary terms.} \\ - The decision procedure could solve the goal with the provision - that additional arguments are supplied for some partially applied - constructors. Any term of an appropriate type will allow the - tactic to successfully solve the goal. Those additional arguments - can be given to {\tt congruence} by filling in the holes in the - terms given in the error message, using the {\tt with} variant - described above. -\end{ErrMsgs} - -\subsection{\tt omega -\tacindex{omega} -\label{omega}} - -The tactic \texttt{omega}, due to Pierre Cr{\'e}gut, -is an automatic decision procedure for Presburger -arithmetic. It solves quantifier-free -formulas built with \verb|~|, \verb|\/|, \verb|/\|, -\verb|->| on top of equalities, inequalities and disequalities on -both the type \texttt{nat} of natural numbers and \texttt{Z} of binary -integers. This tactic must be loaded by the command \texttt{Require Import - Omega}. See the additional documentation about \texttt{omega} -(see Chapter~\ref{OmegaChapter}). - -\subsection{{\tt ring} and {\tt ring\_simplify \term$_1$ \dots\ \term$_n$} -\tacindex{ring} -\tacindex{ring\_simplify} -\comindex{Add Ring}} - -The {\tt ring} tactic solves equations upon polynomial expressions of -a ring (or semi-ring) structure. It proceeds by normalizing both hand -sides of the equation (w.r.t. associativity, commutativity and -distributivity, constant propagation) and comparing syntactically the -results. - -{\tt ring\_simplify} applies the normalization procedure described -above to the terms given. The tactic then replaces all occurrences of -the terms given in the conclusion of the goal by their normal -forms. If no term is given, then the conclusion should be an equation -and both hand sides are normalized. - -See Chapter~\ref{ring} for more information on the tactic and how to -declare new ring structures. - -\subsection{{\tt field}, {\tt field\_simplify \term$_1$\dots\ \term$_n$} - and {\tt field\_simplify\_eq} -\tacindex{field} -\tacindex{field\_simplify} -\tacindex{field\_simplify\_eq} -\comindex{Add Field}} - -The {\tt field} tactic is built on the same ideas as {\tt ring}: this -is a reflexive tactic that solves or simplifies equations in a field -structure. The main idea is to reduce a field expression (which is an -extension of ring expressions with the inverse and division -operations) to a fraction made of two polynomial expressions. - -Tactic {\tt field} is used to solve subgoals, whereas {\tt - field\_simplify \term$_1$\dots\term$_n$} replaces the provided terms -by their reduced fraction. {\tt field\_simplify\_eq} applies when the -conclusion is an equation: it simplifies both hand sides and multiplies -so as to cancel denominators. So it produces an equation without -division nor inverse. - -All of these 3 tactics may generate a subgoal in order to prove that -denominators are different from zero. - -See Chapter~\ref{ring} for more information on the tactic and how to -declare new field structures. - -\Example -\begin{coq_example*} -Require Import Reals. -Goal forall x y:R, - (x * y > 0)%R -> - (x * (1 / x + x / (x + y)))%R = - ((- 1 / y) * y * (- x * (x / (x + y)) - 1))%R. -\end{coq_example*} - -\begin{coq_example} -intros; field. -\end{coq_example} - -\begin{coq_eval} -Reset Initial. -\end{coq_eval} - -\SeeAlso file {\tt plugins/setoid\_ring/RealField.v} for an example of instantiation,\\ -\phantom{\SeeAlso}theory {\tt theories/Reals} for many examples of use of {\tt -field}. - -\subsection{\tt fourier -\tacindex{fourier}} - -This tactic written by Lo{\"\i}c Pottier solves linear inequalities on -real numbers using Fourier's method~\cite{Fourier}. This tactic must -be loaded by {\tt Require Import Fourier}. - -\Example -\begin{coq_example*} -Require Import Reals. -Require Import Fourier. -Goal forall x y:R, (x < y)%R -> (y + 1 >= x - 1)%R. -\end{coq_example*} - -\begin{coq_example} -intros; fourier. -\end{coq_example} - -\begin{coq_eval} -Reset Initial. -\end{coq_eval} - -\subsection{\tt autorewrite with \ident$_1$ \dots \ident$_n$. -\label{tactic:autorewrite} -\tacindex{autorewrite}} - -This tactic \footnote{The behavior of this tactic has much changed compared to -the versions available in the previous distributions (V6). This may cause -significant changes in your theories to obtain the same result. As a drawback -of the re-engineering of the code, this tactic has also been completely revised -to get a very compact and readable version.} carries out rewritings according -the rewriting rule bases {\tt \ident$_1$ \dots \ident$_n$}. - -Each rewriting rule of a base \ident$_i$ is applied to the main subgoal until -it fails. Once all the rules have been processed, if the main subgoal has -progressed (e.g., if it is distinct from the initial main goal) then the rules -of this base are processed again. If the main subgoal has not progressed then -the next base is processed. For the bases, the behavior is exactly similar to -the processing of the rewriting rules. - -The rewriting rule bases are built with the {\tt Hint~Rewrite} vernacular -command. - -\Warning{} This tactic may loop if you build non terminating rewriting systems. - -\begin{Variant} -\item {\tt autorewrite with \ident$_1$ \dots \ident$_n$ using \tac}\\ -Performs, in the same way, all the rewritings of the bases {\tt \ident$_1$ $...$ -\ident$_n$} applying {\tt \tac} to the main subgoal after each rewriting step. - -\item \texttt{autorewrite with {\ident$_1$} \dots \ident$_n$ in {\qualid}} - - Performs all the rewritings in hypothesis {\qualid}. -\item \texttt{autorewrite with {\ident$_1$} \dots \ident$_n$ in {\qualid} using \tac} - - Performs all the rewritings in hypothesis {\qualid} applying {\tt - \tac} to the main subgoal after each rewriting step. - -\item \texttt{autorewrite with {\ident$_1$} \dots \ident$_n$ in \textit{clause}} - Performs all the rewritings in the clause \textit{clause}. \\ - The \textit{clause} argument must not contain any \texttt{type of} nor \texttt{value of}. - -\end{Variant} - -\SeeAlso Section~\ref{HintRewrite} for feeding the database of lemmas used by {\tt autorewrite}. - -\SeeAlso Section~\ref{autorewrite-example} for examples showing the use of -this tactic. - -% En attente d'un moyen de valoriser les fichiers de demos -%\SeeAlso file \texttt{contrib/Rocq/DEMOS/Demo\_AutoRewrite.v} - -\section{Controlling automation} - -\subsection{The hints databases for {\tt auto} and {\tt eauto} -\index{Hints databases} -\label{Hints-databases} -\comindex{Hint}} - -The hints for \texttt{auto} and \texttt{eauto} are stored in -databases. Each database maps head symbols to a list of hints. One can -use the command \texttt{Print Hint \ident} to display the hints -associated to the head symbol \ident{} (see \ref{PrintHint}). Each -hint has a cost that is an nonnegative integer, and an optional pattern. -The hints with lower cost are tried first. A hint is tried by -\texttt{auto} when the conclusion of the current goal -matches its pattern or when it has no pattern. - -\subsubsection*{Creating Hint databases - \label{CreateHintDb}\comindex{CreateHintDb}} - -One can optionally declare a hint database using the command -\texttt{Create HintDb}. If a hint is added to an unknown database, it -will be automatically created. - -\medskip -\texttt{Create HintDb} {\ident} [\texttt{discriminated}] -\medskip - -This command creates a new database named \ident. -The database is implemented by a Discrimination Tree (DT) that serves as -an index of all the lemmas. The DT can use transparency information to decide -if a constant should be indexed or not (c.f. \ref{HintTransparency}), -making the retrieval more efficient. -The legacy implementation (the default one for new databases) uses the -DT only on goals without existentials (i.e., auto goals), for non-Immediate -hints and do not make use of transparency hints, putting more work on the -unification that is run after retrieval (it keeps a list of the lemmas -in case the DT is not used). The new implementation enabled by -the {\tt discriminated} option makes use of DTs in all cases and takes -transparency information into account. However, the order in which hints -are retrieved from the DT may differ from the order in which they were -inserted, making this implementation observationaly different from the -legacy one. - -\begin{Variants} -\item\texttt{Local Hint} \textsl{hint\_definition} \texttt{:} - \ident$_1$ \ldots\ \ident$_n$ - - This is used to declare a hint database that must not be exported to the other - modules that require and import the current module. Inside a - section, the option {\tt Local} is useless since hints do not - survive anyway to the closure of sections. - -\end{Variants} - -The general -command to add a hint to some database \ident$_1$, \dots, \ident$_n$ is: -\begin{tabbing} - \texttt{Hint} \textsl{hint\_definition} \texttt{:} \ident$_1$ \ldots\ \ident$_n$ -\end{tabbing} -where {\sl hint\_definition} is one of the following expressions: - -\begin{itemize} -\item \texttt{Resolve} {\term} - \comindex{Hint Resolve} - - This command adds {\tt apply {\term}} to the hint list - with the head symbol of the type of \term. The cost of that hint is - the number of subgoals generated by {\tt apply {\term}}. - - In case the inferred type of \term\ does not start with a product the - tactic added in the hint list is {\tt exact {\term}}. In case this - type can be reduced to a type starting with a product, the tactic {\tt - apply {\term}} is also stored in the hints list. - - If the inferred type of \term\ contains a dependent - quantification on a predicate, it is added to the hint list of {\tt - eapply} instead of the hint list of {\tt apply}. In this case, a - warning is printed since the hint is only used by the tactic {\tt - eauto} (see \ref{eauto}). A typical example of a hint that is used - only by \texttt{eauto} is a transitivity lemma. - - \begin{ErrMsgs} - \item \errindex{Bound head variable} - - The head symbol of the type of {\term} is a bound variable such - that this tactic cannot be associated to a constant. - - \item \term\ \errindex{cannot be used as a hint} - - The type of \term\ contains products over variables which do not - appear in the conclusion. A typical example is a transitivity axiom. - In that case the {\tt apply} tactic fails, and thus is useless. - - \end{ErrMsgs} - - \begin{Variants} - - \item \texttt{Resolve} {\term$_1$} \dots {\term$_m$} - - Adds each \texttt{Resolve} {\term$_i$}. - - \end{Variants} - -\item \texttt{Immediate {\term}} -\comindex{Hint Immediate} - - This command adds {\tt apply {\term}; trivial} to the hint list - associated with the head symbol of the type of {\ident} in the given - database. This tactic will fail if all the subgoals generated by - {\tt apply {\term}} are not solved immediately by the {\tt trivial} - tactic (which only tries tactics with cost $0$). - - This command is useful for theorems such as the symmetry of equality - or $n+1=m+1 \to n=m$ that we may like to introduce with a - limited use in order to avoid useless proof-search. - - The cost of this tactic (which never generates subgoals) is always 1, - so that it is not used by {\tt trivial} itself. - - \begin{ErrMsgs} - - \item \errindex{Bound head variable} - - \item \term\ \errindex{cannot be used as a hint} - - \end{ErrMsgs} - - \begin{Variants} - - \item \texttt{Immediate} {\term$_1$} \dots {\term$_m$} - - Adds each \texttt{Immediate} {\term$_i$}. - - \end{Variants} - -\item \texttt{Constructors} {\ident} -\comindex{Hint Constructors} - - If {\ident} is an inductive type, this command adds all its - constructors as hints of type \texttt{Resolve}. Then, when the - conclusion of current goal has the form \texttt{({\ident} \dots)}, - \texttt{auto} will try to apply each constructor. - - \begin{ErrMsgs} - - \item {\ident} \errindex{is not an inductive type} - - \item {\ident} \errindex{not declared} - - \end{ErrMsgs} - - \begin{Variants} - - \item \texttt{Constructors} {\ident$_1$} \dots {\ident$_m$} - - Adds each \texttt{Constructors} {\ident$_i$}. - - \end{Variants} - -\item \texttt{Unfold} {\qualid} -\comindex{Hint Unfold} - - This adds the tactic {\tt unfold {\qualid}} to the hint list that - will only be used when the head constant of the goal is \ident. Its - cost is 4. - - \begin{Variants} - - \item \texttt{Unfold} {\ident$_1$} \dots {\ident$_m$} - - Adds each \texttt{Unfold} {\ident$_i$}. - - \end{Variants} - -\item \texttt{Transparent}, \texttt{Opaque} {\qualid} -\label{HintTransparency} -\comindex{Hint Transparent} -\comindex{Hint Opaque} - - This adds a transparency hint to the database, making {\tt {\qualid}} - a transparent or opaque constant during resolution. This information - is used during unification of the goal with any lemma in the database - and inside the discrimination network to relax or constrain it in the - case of \texttt{discriminated} databases. - - \begin{Variants} - - \item \texttt{Transparent}, \texttt{Opaque} {\ident$_1$} \dots {\ident$_m$} - - Declares each {\ident$_i$} as a transparent or opaque constant. - - \end{Variants} - -\item \texttt{Extern \num\ [\pattern]\ => }\textsl{tactic} -\comindex{Hint Extern} - - This hint type is to extend \texttt{auto} with tactics other than - \texttt{apply} and \texttt{unfold}. For that, we must specify a - cost, an optional pattern and a tactic to execute. Here is an example: - -\begin{quotation} -\begin{verbatim} -Hint Extern 4 (~(_ = _)) => discriminate. -\end{verbatim} -\end{quotation} - - Now, when the head of the goal is a disequality, \texttt{auto} will - try \texttt{discriminate} if it does not manage to solve the goal - with hints with a cost less than 4. - - One can even use some sub-patterns of the pattern in the tactic - script. A sub-pattern is a question mark followed by an ident, like - \texttt{?X1} or \texttt{?X2}. Here is an example: - -% Require EqDecide. -\begin{coq_example*} -Require Import List. -\end{coq_example*} -\begin{coq_example} -Hint Extern 5 ({?X1 = ?X2} + {?X1 <> ?X2}) => - generalize X1, X2; decide equality : eqdec. -Goal -forall a b:list (nat * nat), {a = b} + {a <> b}. -info auto with eqdec. -\end{coq_example} -\begin{coq_eval} -Abort. -\end{coq_eval} - -\end{itemize} - -\Rem One can use an \texttt{Extern} hint with no pattern to do -pattern-matching on hypotheses using \texttt{match goal with} inside -the tactic. - -\begin{Variants} -\item \texttt{Hint} \textsl{hint\_definition} - - No database name is given: the hint is registered in the {\tt core} - database. - -\item\texttt{Hint Local} \textsl{hint\_definition} \texttt{:} - \ident$_1$ \ldots\ \ident$_n$ - - This is used to declare hints that must not be exported to the other - modules that require and import the current module. Inside a - section, the option {\tt Local} is useless since hints do not - survive anyway to the closure of sections. - -\item\texttt{Hint Local} \textsl{hint\_definition} - - Idem for the {\tt core} database. - -\end{Variants} - -% There are shortcuts that allow to define several goal at once: - -% \begin{itemize} -% \item \comindex{Hints Resolve}\texttt{Hints Resolve \ident$_1$ \dots\ \ident$_n$ : \ident.}\\ -% This command is a shortcut for the following ones: -% \begin{quotation} -% \noindent\texttt{Hint \ident$_1$ : \ident\ := Resolve \ident$_1$}\\ -% \dots\\ -% \texttt{Hint \ident$_1$ : \ident := Resolve \ident$_1$} -% \end{quotation} -% Notice that the hint name is the same that the theorem given as -% hint. -% \item \comindex{Hints Immediate}\texttt{Hints Immediate \ident$_1$ \dots\ \ident$_n$ : \ident.}\\ -% \item \comindex{Hints Unfold}\texttt{Hints Unfold \qualid$_1$ \dots\ \qualid$_n$ : \ident.}\\ -% \end{itemize} - -%\begin{Warnings} -% \item \texttt{Overriding hint named \dots\ in database \dots} -%\end{Warnings} - - - -\subsection{Hint databases defined in the \Coq\ standard library} - -Several hint databases are defined in the \Coq\ standard library. The -actual content of a database is the collection of the hints declared -to belong to this database in each of the various modules currently -loaded. Especially, requiring new modules potentially extend a -database. At {\Coq} startup, only the {\tt core} and {\tt v62} -databases are non empty and can be used. - -\begin{description} - -\item[\tt core] This special database is automatically used by - \texttt{auto}. It contains only basic lemmas about negation, - conjunction, and so on from. Most of the hints in this database come - from the \texttt{Init} and \texttt{Logic} directories. - -\item[\tt arith] This database contains all lemmas about Peano's - arithmetic proved in the directories \texttt{Init} and - \texttt{Arith} - -\item[\tt zarith] contains lemmas about binary signed integers from - the directories \texttt{theories/ZArith}. When required, the module - {\tt Omega} also extends the database {\tt zarith} with a high-cost - hint that calls {\tt omega} on equations and inequalities in {\tt - nat} or {\tt Z}. - -\item[\tt bool] contains lemmas about booleans, mostly from directory - \texttt{theories/Bool}. - -\item[\tt datatypes] is for lemmas about lists, streams and so on that - are mainly proved in the \texttt{Lists} subdirectory. - -\item[\tt sets] contains lemmas about sets and relations from the - directories \texttt{Sets} and \texttt{Relations}. - -\item[\tt typeclass\_instances] contains all the type class instances - declared in the environment, including those used for \texttt{setoid\_rewrite}, - from the \texttt{Classes} directory. -\end{description} - -There is also a special database called {\tt v62}. It collects all -hints that were declared in the versions of {\Coq} prior to version -6.2.4 when the databases {\tt core}, {\tt arith}, and so on were -introduced. The purpose of the database {\tt v62} is to ensure -compatibility with further versions of {\Coq} for developments done in -versions prior to 6.2.4 ({\tt auto} being replaced by {\tt auto with v62}). -The database {\tt v62} is intended not to be extended (!). It is not -included in the hint databases list used in the {\tt auto with *} tactic. - -Furthermore, you are advised not to put your own hints in the -{\tt core} database, but use one or several databases specific to your -development. - -\subsection{\tt Print Hint -\label{PrintHint} -\comindex{Print Hint}} - -This command displays all hints that apply to the current goal. It -fails if no proof is being edited, while the two variants can be used at -every moment. - -\begin{Variants} - -\item {\tt Print Hint {\ident} } - - This command displays only tactics associated with \ident\ in the - hints list. This is independent of the goal being edited, so this - command will not fail if no goal is being edited. - -\item {\tt Print Hint *} - - This command displays all declared hints. - -\item {\tt Print HintDb {\ident} } -\label{PrintHintDb} -\comindex{Print HintDb} - - This command displays all hints from database \ident. - -\end{Variants} - -\subsection{\tt Hint Rewrite \term$_1$ \dots \term$_n$ : \ident -\label{HintRewrite} -\comindex{Hint Rewrite}} - -This vernacular command adds the terms {\tt \term$_1$ \dots \term$_n$} -(their types must be equalities) in the rewriting base {\tt \ident} -with the default orientation (left to right). Notice that the -rewriting bases are distinct from the {\tt auto} hint bases and that -{\tt auto} does not take them into account. - -This command is synchronous with the section mechanism (see \ref{Section}): -when closing a section, all aliases created by \texttt{Hint Rewrite} in that -section are lost. Conversely, when loading a module, all \texttt{Hint Rewrite} -declarations at the global level of that module are loaded. - -\begin{Variants} -\item {\tt Hint Rewrite -> \term$_1$ \dots \term$_n$ : \ident}\\ -This is strictly equivalent to the command above (we only make explicit the -orientation which otherwise defaults to {\tt ->}). - -\item {\tt Hint Rewrite <- \term$_1$ \dots \term$_n$ : \ident}\\ -Adds the rewriting rules {\tt \term$_1$ \dots \term$_n$} with a right-to-left -orientation in the base {\tt \ident}. - -\item {\tt Hint Rewrite \term$_1$ \dots \term$_n$ using {\tac} : {\ident}}\\ -When the rewriting rules {\tt \term$_1$ \dots \term$_n$} in {\tt \ident} will -be used, the tactic {\tt \tac} will be applied to the generated subgoals, the -main subgoal excluded. - -%% \item -%% {\tt Hint Rewrite [ \term$_1$ \dots \term$_n$ ] in \ident}\\ -%% {\tt Hint Rewrite [ \term$_1$ \dots \term$_n$ ] in {\ident} using {\tac}}\\ -%% These are deprecated syntactic variants for -%% {\tt Hint Rewrite \term$_1$ \dots \term$_n$ : \ident} and -%% {\tt Hint Rewrite \term$_1$ \dots \term$_n$ using {\tac} : {\ident}}. - -\item \texttt{Print Rewrite HintDb {\ident}} - - This command displays all rewrite hints contained in {\ident}. - -\end{Variants} - -\subsection{Hints and sections -\label{Hint-and-Section}} - -Hints provided by the \texttt{Hint} commands are erased when closing a -section. Conversely, all hints of a module \texttt{A} that are not -defined inside a section (and not defined with option {\tt Local}) become -available when the module {\tt A} is imported (using -e.g. \texttt{Require Import A.}). - -\subsection{Setting implicit automation tactics} - -\subsubsection[\tt Proof with {\tac}.]{\tt Proof with {\tac}.\label{ProofWith} -\comindex{Proof with}} - - This command may be used to start a proof. It defines a default - tactic to be used each time a tactic command {\tac$_1$} is ended by - ``\verb#...#''. In this case the tactic command typed by the user is - equivalent to \tac$_1$;{\tac}. - -\SeeAlso {\tt Proof.} in Section~\ref{BeginProof}. - -\subsubsection[\tt Declare Implicit Tactic {\tac}.]{\tt Declare Implicit Tactic {\tac}.\comindex{Declare Implicit Tactic}} - -This command declares a tactic to be used to solve implicit arguments -that {\Coq} does not know how to solve by unification. It is used -every time the term argument of a tactic has one of its holes not -fully resolved. - -Here is an example: - -\begin{coq_example} -Parameter quo : nat -> forall n:nat, n<>0 -> nat. -Notation "x // y" := (quo x y _) (at level 40). - -Declare Implicit Tactic assumption. -Goal forall n m, m<>0 -> { q:nat & { r | q * m + r = n } }. -intros. -exists (n // m). -\end{coq_example} - -The tactic {\tt exists (n // m)} did not fail. The hole was solved by -{\tt assumption} so that it behaved as {\tt exists (quo n m H)}. - -\section{Generation of induction principles with {\tt Scheme} -\label{Scheme} -\index{Schemes} -\comindex{Scheme}} - -The {\tt Scheme} command is a high-level tool for generating -automatically (possibly mutual) induction principles for given types -and sorts. Its syntax follows the schema: -\begin{quote} -{\tt Scheme {\ident$_1$} := Induction for \ident'$_1$ Sort {\sort$_1$} \\ - with\\ - \mbox{}\hspace{0.1cm} \dots\\ - with {\ident$_m$} := Induction for {\ident'$_m$} Sort - {\sort$_m$}} -\end{quote} -where \ident'$_1$ \dots\ \ident'$_m$ are different inductive type -identifiers belonging to the same package of mutual inductive -definitions. This command generates {\ident$_1$}\dots{} {\ident$_m$} -to be mutually recursive definitions. Each term {\ident$_i$} proves a -general principle of mutual induction for objects in type {\term$_i$}. - -\begin{Variants} -\item {\tt Scheme {\ident$_1$} := Minimality for \ident'$_1$ Sort {\sort$_1$} \\ - with\\ - \mbox{}\hspace{0.1cm} \dots\ \\ - with {\ident$_m$} := Minimality for {\ident'$_m$} Sort - {\sort$_m$}} - - Same as before but defines a non-dependent elimination principle more - natural in case of inductively defined relations. - -\item {\tt Scheme Equality for \ident$_1$\comindex{Scheme Equality}} - - Tries to generate a boolean equality and a proof of the - decidability of the usual equality. - -\item {\tt Scheme Induction for \ident$_1$ Sort {\sort$_1$} \\ - with\\ - \mbox{}\hspace{0.1cm} \dots\\ - with Induction for {\ident$_m$} Sort - {\sort$_m$}} - - If you do not provide the name of the schemes, they will be automatically - computed from the sorts involved (works also with Minimality). - -\end{Variants} - -\SeeAlso Section~\ref{Scheme-examples} - -\subsection{Automatic declaration of schemes} -\comindex{Set Equality Schemes} -\comindex{Set Elimination Schemes} -It is possible to deactivate the automatic declaration of the induction - principles when defining a new inductive type with the - {\tt Unset Elimination Schemes} command. It may be -reactivated at any time with {\tt Set Elimination Schemes}. -\\ - -You can also activate the automatic declaration of those boolean equalities -(see the second variant of {\tt Scheme}) with the {\tt Set Equality Schemes} - command. However you have to be careful with this option since -\Coq~ may now reject well-defined inductive types because it cannot compute -a boolean equality for them. - -\subsection{\tt Combined Scheme\label{CombinedScheme} -\comindex{Combined Scheme}} -The {\tt Combined Scheme} command is a tool for combining -induction principles generated by the {\tt Scheme} command. -Its syntax follows the schema : - -\noindent -{\tt Combined Scheme {\ident$_0$} from {\ident$_1$}, .., {\ident$_n$}}\\ -\ident$_1$ \ldots \ident$_n$ are different inductive principles that must belong to -the same package of mutual inductive principle definitions. This command -generates {\ident$_0$} to be the conjunction of the principles: it is -built from the common premises of the principles and concluded by the -conjunction of their conclusions. - -\SeeAlso Section~\ref{CombinedScheme-examples} - -\section{Generation of induction principles with {\tt Functional Scheme} -\label{FunScheme} -\comindex{Functional Scheme}} - -The {\tt Functional Scheme} command is a high-level experimental -tool for generating automatically induction principles -corresponding to (possibly mutually recursive) functions. Its -syntax follows the schema: -\begin{quote} -{\tt Functional Scheme {\ident$_1$} := Induction for \ident'$_1$ Sort {\sort$_1$} \\ - with\\ - \mbox{}\hspace{0.1cm} \dots\ \\ - with {\ident$_m$} := Induction for {\ident'$_m$} Sort - {\sort$_m$}} -\end{quote} -where \ident'$_1$ \dots\ \ident'$_m$ are different mutually defined function -names (they must be in the same order as when they were defined). -This command generates the induction principles -\ident$_1$\dots\ident$_m$, following the recursive structure and case -analyses of the functions \ident'$_1$ \dots\ \ident'$_m$. - - -\paragraph{\texttt{Functional Scheme}} -There is a difference between obtaining an induction scheme by using -\texttt{Functional Scheme} on a function defined by \texttt{Function} -or not. Indeed \texttt{Function} generally produces smaller -principles, closer to the definition written by the user. - - -\SeeAlso Section~\ref{FunScheme-examples} - - -\section{Simple tactic macros -\index{Tactic macros} -\comindex{Tactic Definition} -\label{TacticDefinition}} - -A simple example has more value than a long explanation: - -\begin{coq_example} -Ltac Solve := simpl; intros; auto. -Ltac ElimBoolRewrite b H1 H2 := - elim b; [ intros; rewrite H1; eauto | intros; rewrite H2; eauto ]. -\end{coq_example} - -The tactics macros are synchronous with the \Coq\ section mechanism: -a tactic definition is deleted from the current environment -when you close the section (see also \ref{Section}) -where it was defined. If you want that a -tactic macro defined in a module is usable in the modules that -require it, you should put it outside of any section. - -Chapter~\ref{TacticLanguage} gives examples of more complex -user-defined tactics. - - -% $Id: RefMan-tac.tex 14762 2011-12-04 20:48:36Z herbelin $ - -%%% Local Variables: -%%% mode: latex -%%% TeX-master: "Reference-Manual" -%%% TeX-master: "Reference-Manual" -%%% End: |