| Commit message (Collapse) | Author | Age |
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Originally, rel-context was represented as:
Context.rel_context = Names.Name.t * Constr.t option * Constr.t
Now it is represented as:
Context.Rel.t = LocalAssum of Names.Name.t * Constr.t
| LocalDef of Names.Name.t * Constr.t * Constr.t
Originally, named-context was represented as:
Context.named_context = Names.Id.t * Constr.t option * Constr.t
Now it is represented as:
Context.Named.t = LocalAssum of Names.Id.t * Constr.t
| LocalDef of Names.Id.t * Constr.t * Constr.t
Motivation:
(1) In "tactics/hipattern.ml4" file we define "test_strict_disjunction"
function which looked like this:
let test_strict_disjunction n lc =
Array.for_all_i (fun i c ->
match (prod_assum (snd (decompose_prod_n_assum n c))) with
| [_,None,c] -> isRel c && Int.equal (destRel c) (n - i)
| _ -> false) 0 lc
Suppose that you do not know about rel-context and named-context.
(that is the case of people who just started to read the source code)
Merlin would tell you that the type of the value you are destructing
by "match" is:
'a * 'b option * Constr.t (* worst-case scenario *)
or
Named.Name.t * Constr.t option * Constr.t (* best-case scenario (?) *)
To me, this is akin to wearing an opaque veil.
It is hard to figure out the meaning of the values you are looking at.
In particular, it is hard to discover the connection between the value
we are destructing above and the datatypes and functions defined
in the "kernel/context.ml" file.
In this case, the connection is there, but it is not visible
(between the function above and the "Context" module).
------------------------------------------------------------------------
Now consider, what happens when the reader see the same function
presented in the following form:
let test_strict_disjunction n lc =
Array.for_all_i (fun i c ->
match (prod_assum (snd (decompose_prod_n_assum n c))) with
| [LocalAssum (_,c)] -> isRel c && Int.equal (destRel c) (n - i)
| _ -> false) 0 lc
If the reader haven't seen "LocalAssum" before, (s)he can use Merlin
to jump to the corresponding definition and learn more.
In this case, the connection is there, and it is directly visible
(between the function above and the "Context" module).
(2) Also, if we already have the concepts such as:
- local declaration
- local assumption
- local definition
and we describe these notions meticulously in the Reference Manual,
then it is a real pity not to reinforce the connection
of the actual code with the abstract description we published.
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(see 2e3ae20fe1e): test was only relevant in the case of explicitly
given occurrence numbers.
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The main change is that selection of subterm is made similar whether
the given term is fully applied or not.
- The selection of subterm now works as follows depending on whether
the "at" is given, of whether the subterm is fully applied or not,
and whether there are incompatible subterms matching the pattern. In
particular, we have:
"at" given
| subterm fully applied
| | incompatible subterms
| | |
Y Y - it works like in 8.4
Y N - this was broken in 8.4 ("at" was ineffective and it was finding
all subterms syntactically equal to the first one which matches)
N Y Y it now finds all subterms like the first one which matches
while in 8.4 it used to fail (I hope it is not a too risky in-draft
for a semantics we would regret...) (e.g. "destruct (S _)" on
goal "S x = S y + S x" now selects the two occurrences of "S x"
while it was failing before)
N Y N it works like in 8.4
N N - it works like in 8.4, selecting all subterms like the
first one which matches
- Note that the "historical" semantics, when looking for a subterm, to
select all subterms that syntactically match the first subterm to
match the pattern (looking from left to right) is now internally called
"like first".
- Selection of subterms can now find the type by pattern-matching (useful e.g.
for "induction (nat_rect _ _ _ _)")
- A version of Unification.w_unify w/o any conversion is used for
finding the subterm: it could be easily replaced by an other
matching algorithm.
In particular, "destruct H" now works on a goal such as "H:True -> x<=y |- P y".
Secondary change is in the interpretation of terms with existential
variables:
- When several arguments are given, interpretation is delayed at the
time of execution
- Because we aim at eventually accepting "edestruct c" with unresolved
holes in c, we need the sigma obtained from c to be an extension of
the sigma of the tactics, while before, we just type-checked c
independently of the sigma of the tactic
- Finishing the resolution of evars (using type classes, candidates,
pending conversion problems) is made slightly cleaner: it now takes
three states: a term is evaluated in state sigma, leading to state
sigma' >= sigma, with evars finally solved in state sigma'' >=
sigma'; we solve evars in the diff of sigma' and sigma and report
the solution in sigma''
- We however renounce to give now a success semantics to "edestruct c"
when "c" has unresolved holes, waiting instead for a decision on
what to do in the case of a similar eapply (see mail to coqdev).
An auxiliary change is that an "in" clause can be attached to each component
of a "destruct t, u, v", etc.
Incidentally, make_abstraction does not do evar resolution itself any longer.
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projections with their eta-expanded constant form.
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into a specific new cleaned file find_subterm.ml.
This makes things clearer but also solves some dependencies problem
between Evd, Termops and Pretype_errors.
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Matej Kosik
Maxime Dénès
Pierre-Marie Pédrot
Hugo Herbelin
Matthieu Sozeau