Friday 31 October 2008

Coq Extension


(*
NoConfusion_Foo (P : Type) [indices] (u v : Foo [indices]) :=
match u, v with
| Foo x y z, Foo x y z => (x == x' -> y == y' -> z == z' -> P) -> P
| ...
| Chalk*, Cheese* => P
end
*)

(*
noConfusion_Foo (P : Type) [indices] (u v : Foo [indices]) : u == v -> NoConfusion_foo P [indices] u v.
*)

open Univ
open Inductive
open Util
open Coqlib

let ith_univ i = make_univ (make_dirpath [id_of_string"implicit"], i)
let implicit_type i = mkSort (Type (ith_univ i))
let raw_type i = RSort (dummy_loc, RType (Some (ith_univ i)))

let coq_heq_ref = lazy (Coqlib.coq_reference "mkHEq" ["Logic";"JMeq"] "JMeq")

let construct_no_conf_body env ind mind =
let ctr_types = arities_of_constructors ind mind in
let n_ctr_types = Array.length ctr_types in
let n_indices = length (snd mind).mind_arity_ctxt in
let indices =
let rec names i = if i > n_indices then [] else RVar (dummy_loc, id_of_string ("e"^string_of_int i)) :: names (i+1) in names 1 in
let abstract_indices x =
let rec abs i =
if i > n_indices
then x
else RLambda (dummy_loc, Name (id_of_string ("e"^string_of_int i)), Explicit, RHole (dummy_loc, BinderType Anonymous), abs (i+1)) in
abs 1 in
Pretyping.Default.understand Evd.empty env
(RLambda (dummy_loc, Name (id_of_string "P"), Explicit, raw_type 1,
abstract_indices
(RLambda (dummy_loc, Name (id_of_string "u"), Explicit, RApp (dummy_loc, RRef (dummy_loc, IndRef ind), indices),
(RLambda (dummy_loc, Name (id_of_string "v"), Explicit, RApp (dummy_loc, RRef (dummy_loc, IndRef ind), indices),
RCases (dummy_loc, MatchStyle, None,
[(RVar (dummy_loc, (id_of_string "u")), (Anonymous, None));(RVar (dummy_loc, (id_of_string "v")), (Anonymous, None))],
(Array.to_list (Array.mapi (fun i ty_i ->
let ctr = (ind, i+1) in
let ctr_args = constructor_nrealhyps env ctr in
let rec spread n i = if i = 0 then [] else (PatVar (dummy_loc, Name (id_of_string (n^string_of_int i)))) :: spread n (i-1) in
let left_patterns = List.rev (spread "i" ctr_args) in
let right_patterns = List.rev (spread "j" ctr_args) in
let rec assume_eqs n x = if n > ctr_args
then x
else RProd (dummy_loc, Anonymous, Explicit,
RApp (dummy_loc, RRef (dummy_loc, Lazy.force coq_heq_ref),
[RHole (dummy_loc, BinderType Anonymous); RVar (dummy_loc, id_of_string ("i"^string_of_int n));
RHole (dummy_loc, BinderType Anonymous); RVar (dummy_loc, id_of_string ("j"^string_of_int n))]),
assume_eqs (n+1) x) in
(dummy_loc, [id_of_string "foo";id_of_string "bar"],
[PatCstr (dummy_loc, ctr, left_patterns, Anonymous);PatCstr (dummy_loc, ctr, right_patterns, Anonymous)],
RProd (dummy_loc, Anonymous, Explicit,
assume_eqs 1 (RVar (dummy_loc, id_of_string "P")), RVar (dummy_loc, id_of_string "P")))) ctr_types) @
if n_ctr_types = 1
then []
else [(dummy_loc, [id_of_string "foo";id_of_string "bar"],
[PatVar (dummy_loc, Anonymous);PatVar (dummy_loc, Anonymous)],
RVar (dummy_loc, id_of_string "P"))]))))))))

let construct_no_conf_declaration env ind mind =
DefinitionEntry
{ const_entry_body = construct_no_conf_body env ind mind;
const_entry_type = None;
const_entry_opaque = false;
const_entry_boxed = false }, IsDefinition Definition

let construct_little_no_conf env ind mind little_no_conf no_conf =
let n_indices = length (snd mind).mind_arity_ctxt in
let indices =
let rec names i = if i > n_indices then [] else RVar (dummy_loc, id_of_string ("e"^string_of_int i)) :: names (i+1) in names 1 in
let abstract_indices x =
let rec abs i =
if i > n_indices
then x
else RProd (dummy_loc, Name (id_of_string ("e"^string_of_int i)), Explicit, RHole (dummy_loc, BinderType Anonymous), abs (i+1)) in
abs 1 in
let little_no_conf_type = Pretyping.Default.understand Evd.empty env
(RProd (dummy_loc, Name (id_of_string "P"), Explicit, raw_type 1,
abstract_indices
(RProd (dummy_loc, Name (id_of_string "u"), Explicit, RApp (dummy_loc, RRef (dummy_loc, IndRef ind), indices),
(RProd (dummy_loc, Name (id_of_string "v"), Explicit, RApp (dummy_loc, RRef (dummy_loc, IndRef ind), indices),
(RProd (dummy_loc, Name (id_of_string "eql"), Explicit,
RApp (dummy_loc, RRef (dummy_loc, Lazy.force coq_heq_ref),
[RHole (dummy_loc, BinderType Anonymous); RVar (dummy_loc, id_of_string "u");
RHole (dummy_loc, BinderType Anonymous); RVar (dummy_loc, id_of_string "v")]),
RApp (dummy_loc, RRef (dummy_loc, no_conf),
([RVar (dummy_loc, id_of_string "P")] @
indices @
[RVar (dummy_loc, id_of_string "u");
RVar (dummy_loc, id_of_string "v")])))))))))) in
try
let _ =
Pfedit.start_proof little_no_conf (Global, DefinitionBody Definition)
(named_context_val env)
little_no_conf_type
(fun _ _ -> ());
Pfedit.by (tclTHENSEQ
[intros;
simplest_elim (mkVar (id_of_string "eql"));
simplest_elim (mkVar (id_of_string "u"));
simpl_in_concl;
Tauto.tauto]) in
let _,(const,_,_) = Pfedit.cook_proof (fun _ -> ()) in
Pfedit.delete_current_proof ();
DefinitionEntry const, IsDefinition Definition
with e ->
Pfedit.delete_current_proof ();
msg (str "Could not prove noConfusion, this is a serious (unexpected) problem!");
raise e

let no_confusion i =
check_required_library ["Coq";"Logic";"JMeq"];
let env = Global.env () in
let istr = string_of_id i in
try
match Nametab.locate (qualid_of_string istr) with
| IndRef ind ->
let mind = lookup_mind_specif env ind in
let no_conf = add_prefix "NoConfusion_" i in
let little_no_conf = add_prefix "noConfusion_" i in
(* msg (print_constr (construct_no_conf_body env ind mind)); TODO: Print a better message *)
let _ = Declare.declare_constant no_conf (construct_no_conf_declaration env ind mind) in
let no_conf_ty = Nametab.locate (qualid_of_string ("NoConfusion_"^istr)) in
let env = Global.env () in
Declare.declare_constant little_no_conf (construct_little_no_conf env ind mind little_no_conf no_conf_ty);
()
| _ -> msg (str (istr^" is not an inductive."))
with Not_found -> msg (str ("Inductive "^istr^" not found in global environment."))


VERNAC COMMAND EXTEND Derive_NoConfusion
| [ "Derive" "NoConfusion" ident(i) ] -> [ no_confusion i ]
END

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