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diff --git a/doc/sphinx/README.rst b/doc/sphinx/README.rst new file mode 100644 index 000000000..35a605ddd --- /dev/null +++ b/doc/sphinx/README.rst @@ -0,0 +1,395 @@ +============================= + Documenting Coq with Sphinx +============================= + +.. + README.rst is auto-generated from README.template.rst and the coqrst docs; + use ``doc/tools/coqrst/regen_readme.py`` to rebuild it. + +Coq's reference manual is written in `reStructuredText <http://www.sphinx-doc.org/en/master/usage/restructuredtext/basics.html>`_ (“reST”), and compiled with `Sphinx <http://www.sphinx-doc.org/en/master/>`_. + +In addition to standard reST directives (a directive is similar to a LaTeX environment) and roles (a role is similar to a LaTeX command), the ``coqrst`` plugin loaded by the documentation uses a custom *Coq domain* — a set of Coq-specific directives that define *objects* like tactics, commands (vernacs), warnings, etc. —, some custom *directives*, and a few custom *roles*. Finally, this manual uses a small DSL to describe tactic invocations and commands. + +Coq objects +=========== + +Our Coq domain define multiple `objects`_. Each object has a *signature* (think *type signature*), followed by an optional body (a description of that object). The following example defines two objects: a variant of the ``simpl`` tactic, and an error that it may raise:: + + .. tacv:: simpl @pattern at {+ @num} + :name: simpl_at + + This applies ``simpl`` only to the :n:`{+ @num}` occurrences of the subterms + matching :n:`@pattern` in the current goal. + + .. exn:: Too few occurrences + :undocumented: + +Objects are automatically collected into indices, and can be linked to using the role version of the object's directive. For example, you could link to the tactic variant above using ``:tacv:`simpl_at```, and to its exception using ``:exn:`Too few occurrences```. + +Names (link targets) are auto-generated for most simple objects, though they can always be overwritten using a ``:name:`` option, as shown above. + +- Options, errors, warnings have their name set to their signature, with ``...`` replacing all notation bits. For example, the auto-generated name of ``.. exn:: @qualid is not a module`` is ``... is not a module``, and a link to it would take the form ``:exn:`... is not a module```. +- Vernacs (commands) have their name set to the first word of their signature. For example, the auto-generated name of ``Axiom @ident : @term`` is ``Axiom``, and a link to it would take the form ``:cmd:`Axiom```. +- Vernac variants, tactic notations, and tactic variants do not have a default name. + +Most objects should have a body (i.e. a block of indented text following the signature, called “contents” in Sphinx terms). Undocumented objects should have the `:undocumented:` flag instead, as shown above. When multiple objects have a single description, they can be grouped into a single object, like this (semicolons can be used to separate the names of the objects):: + + .. cmdv:: Lemma @ident {? @binders} : @type + Remark @ident {? @binders} : @type + Fact @ident {? @binders} : @type + Corollary @ident {? @binders} : @type + Proposition @ident {? @binders} : @type + :name: Lemma; Remark; Fact; Corollary; Proposition + + These commands are all synonyms of :n:`Theorem @ident {? @binders } : type`. + +Notations +--------- + +The signatures of most objects can be written using a succinct DSL for Coq notations (think regular expressions written with a Lispy syntax). A typical signature might look like ``Hint Extern @num {? @pattern} => @tactic``, which means that the ``Hint Extern`` command takes a number (``num``), followed by an optional pattern, and a mandatory tactic. The language has the following constructs (the full grammar is in `TacticNotations.g </doc/tools/coqrst/notations/TacticNotations.g>`_): + +``@…`` + A placeholder (``@ident``, ``@num``, ``@tactic``\ …) + +``{? …}`` + an optional block + +``{* …}``, ``{+ …}`` + an optional (``*``) or mandatory (``+``) block that can be repeated, with repetitions separated by spaces + +``{*, …}``, ``{+, …}`` + an optional or mandatory repeatable block, with repetitions separated by commas + +``%|``, ``%{``, … + an escaped character (rendered without the leading ``%``) + +.. + FIXME document the new subscript support + +As an exercise, what do the following patterns mean? + +.. code:: + + pattern {+, @term {? at {+ @num}}} + generalize {+, @term at {+ @num} as @ident} + fix @ident @num with {+ (@ident {+ @binder} {? {struct @ident'}} : @type)} + +Objects +------- + +Here is the list of all objects of the Coq domain (The symbol :black_nib: indicates an object whose signature can be written using the notations DSL): + +``.. cmd::`` :black_nib: A Coq command. + Example:: + + .. cmd:: Infix "@symbol" := @term ({+, @modifier}). + + This command is equivalent to :n:`…`. + +``.. cmdv::`` :black_nib: A variant of a Coq command. + Example:: + + .. cmd:: Axiom @ident : @term. + + This command links :token:`term` to the name :token:`term` as its specification in + the global context. The fact asserted by :token:`term` is thus assumed as a + postulate. + + .. cmdv:: Parameter @ident : @term. + + This is equivalent to :n:`Axiom @ident : @term`. + +``.. exn::`` :black_nib: An error raised by a Coq command or tactic. + This commonly appears nested in the ``.. tacn::`` that raises the + exception. + + Example:: + + .. tacv:: assert @form by @tactic + + This tactic applies :n:`@tactic` to solve the subgoals generated by + ``assert``. + + .. exn:: Proof is not complete + + Raised if :n:`@tactic` does not fully solve the goal. + +``.. opt::`` :black_nib: A Coq option. + Example:: + + .. opt:: Nonrecursive Elimination Schemes + + This option controls whether types declared with the keywords + :cmd:`Variant` and :cmd:`Record` get an automatic declaration of the + induction principles. + +``.. prodn::`` :black_nib: Grammar productions. + This is useful if you intend to document individual grammar productions. + Otherwise, use Sphinx's `production lists + <http://www.sphinx-doc.org/en/stable/markup/para.html#directive-productionlist>`_. + +``.. tacn::`` :black_nib: A tactic, or a tactic notation. + Example:: + + .. tacn:: do @num @expr + + :token:`expr` is evaluated to ``v`` which must be a tactic value. … + +``.. tacv::`` :black_nib: A variant of a tactic. + Example:: + + .. tacn:: fail + + This is the always-failing tactic: it does not solve any goal. It is + useful for defining other tacticals since it can be caught by + :tacn:`try`, :tacn:`repeat`, :tacn:`match goal`, or the branching + tacticals. … + + .. tacv:: fail @natural + + The number is the failure level. If no level is specified, it + defaults to 0. … + +``.. thm::`` A theorem. + Example:: + + .. thm:: Bound on the ceiling function + + Let :math:`p` be an integer and :math:`c` a rational constant. Then + :math:`p \ge c \rightarrow p \ge \lceil{c}\rceil`. + +``.. warn::`` :black_nib: An warning raised by a Coq command or tactic.. + Do not mistake this for ``.. warning::``; this directive is for warning + messages produced by Coq. + + + Example:: + + .. warn:: Ambiguous path + + When the coercion :token:`qualid` is added to the inheritance graph, non + valid coercion paths are ignored. + +Coq directives +============== + +In addition to the objects above, the ``coqrst`` Sphinx plugin defines the following directives: + +``.. coqtop::`` A reST directive to describe interactions with Coqtop. + Usage:: + + .. coqtop:: options… + + Coq code to send to coqtop + + Example:: + + .. coqtop:: in reset undo + + Print nat. + Definition a := 1. + + Here is a list of permissible options: + + - Display options + + - ``all``: Display input and output + - ``in``: Display only input + - ``out``: Display only output + - ``none``: Display neither (useful for setup commands) + + - Behavior options + + - ``reset``: Send a ``Reset Initial`` command before running this block + - ``undo``: Send an ``Undo n`` (``n`` = number of sentences) command after + running all the commands in this block + + ``coqtop``\ 's state is preserved across consecutive ``.. coqtop::`` blocks + of the same document (``coqrst`` creates a single ``coqtop`` process per + reST source file). Use the ``reset`` option to reset Coq's state. + +``.. coqdoc::`` A reST directive to display Coqtop-formatted source code. + Usage:: + + .. coqdoc:: + + Coq code to highlight + + Example:: + + .. coqdoc:: + + Definition test := 1. + +``.. example::`` A reST directive for examples. + This behaves like a generic admonition; see + http://docutils.sourceforge.net/docs/ref/rst/directives.html#generic-admonition + for more details. + + Example:: + + .. example:: Adding a hint to a database + + The following adds ``plus_comm`` to the ``plu`` database: + + .. coqdoc:: + + Hint Resolve plus_comm : plu. + +``.. inference::`` A reST directive to format inference rules. + This also serves as a small illustration of the way to create new Sphinx + directives. + + Usage:: + + .. inference:: name + + newline-separated premisses + ------------------------ + conclusion + + Example:: + + .. inference:: Prod-Pro + + \WTEG{T}{s} + s \in \Sort + \WTE{\Gamma::(x:T)}{U}{\Prop} + ----------------------------- + \WTEG{\forall~x:T,U}{\Prop} + +``.. preamble::`` A reST directive for hidden math. + Mostly useful to let MathJax know about `\def`\ s and `\newcommand`\ s. + + Example:: + + .. preamble:: + + \newcommand{\paren}[#1]{\left(#1\right)} + +Coq roles +========= + +In addition to the objects and directives above, the ``coqrst`` Sphinx plugin defines the following roles: + +``:g:`` Coq code. + Use this for Gallina and Ltac snippets:: + + :g:`apply plus_comm; reflexivity` + :g:`Set Printing All.` + :g:`forall (x: t), P(x)` + +``:n:`` Any text using the notation syntax (``@id``, ``{+, …}``, etc.). + Use this to explain tactic equivalences. For example, you might write + this:: + + :n:`generalize @term as @ident` is just like :n:`generalize @term`, but + it names the introduced hypothesis :token:`ident`. + + Note that this example also uses ``:token:``. That's because ``ident`` is + defined in the the Coq manual as a grammar production, and ``:token:`` + creates a link to that. When referring to a placeholder that happens to be + a grammar production, ``:token:`…``` is typically preferable to ``:n:`@…```. + +``:production:`` A grammar production not included in a ``productionlist`` directive. + Useful to informally introduce a production, as part of running text. + + Example:: + + :production:`string` indicates a quoted string. + + You're not likely to use this role very commonly; instead, use a + `production list + <http://www.sphinx-doc.org/en/stable/markup/para.html#directive-productionlist>`_ + and reference its tokens using ``:token:`…```. + +Common mistakes +=============== + +Improper nesting +---------------- + +DO + .. code:: + + .. cmd:: Foo @bar + + Foo the first instance of :token:`bar`\ s. + + .. cmdv:: Foo All + + Foo all the :token:`bar`\ s in + the current context + +DON'T + .. code:: + + .. cmd:: Foo @bar + + Foo the first instance of :token:`bar`\ s. + + .. cmdv:: Foo All + + Foo all the :token:`bar`\ s in + the current context + +You can set the ``report_undocumented_coq_objects`` setting in ``conf.py`` to ``"info"`` or ``"warning"`` to get a list of all Coq objects without a description. + +Overusing ``:token:`` +--------------------- + +DO + .. code:: + + This is equivalent to :n:`Axiom @ident : @term`. + +DON'T + .. code:: + + This is equivalent to ``Axiom`` :token`ident` : :token:`term`. + +Omitting annotations +-------------------- + +DO + .. code:: + + .. tacv:: assert @form as @intro_pattern + +DON'T + .. code:: + + .. tacv:: assert form as intro_pattern + +Tips and tricks +=============== + +Nested lemmas +------------- + +The ``.. coqtop::`` directive does *not* reset Coq after running its contents. That is, the following will create two nested lemmas:: + + .. coqtop:: all + + Lemma l1: 1 + 1 = 2. + + .. coqtop:: all + + Lemma l2: 2 + 2 <> 1. + +Add either ``undo`` to the first block or ``reset`` to the second block to avoid nesting lemmas. + +Abbreviations and macros +------------------------ + +Abbreviations and placeholders for specially-formatted names (like ``|Cic|``, ``|Coq|``, ``|CoqIDE|``, ``|Ltac|``, and ``|Gallina|``) are defined in a `separate file </doc/sphinx/replaces.rst>`_ included by most chapters of the manual. Some useful LaTeX macros are defined in `</doc/sphinx/preamble.rst>`_. + +Emacs +----- + +The ``dev/tools/coqdev.el`` folder contains a convenient Emacs function to quickly insert Sphinx roles and quotes. It takes a single character (one of ``gntm:```), and inserts one of ``:g:``, ``:n:``, ``:t:``, or an arbitrary role, or double quotes. You can also select a region of text, and wrap it in single or double backticks using that function. + +Use the following snippet to bind it to :kbd:`F12` in ``rst-mode``:: + + (with-eval-after-load 'rst + (define-key rst-mode-map (kbd "<f12>") #'coqdev-sphinx-rst-coq-action)) |