path: root/pretyping/pattern.ml

(***********************************************************************)
(*  v      *   The Coq Proof Assistant  /  The Coq Development Team    *)
(* <O___,, *        INRIA-Rocquencourt  &  LRI-CNRS-Orsay              *)
(*   \VV/  *************************************************************)
(*    //   *      This file is distributed under the terms of the      *)
(*         *       GNU Lesser General Public License Version 2.1       *)
(***********************************************************************)

(* $Id$ *)

open Util
open Names
open Nameops
open Term
open Termops
open Reductionops
open Rawterm
open Environ
open Nametab

type constr_pattern =
  | PRef of global_reference
  | PVar of identifier
  | PEvar of existential_key
  | PRel of int
  | PApp of constr_pattern * constr_pattern array
  | PSoApp of int * constr_pattern list
  | PLambda of name * constr_pattern * constr_pattern
  | PProd of name * constr_pattern * constr_pattern
  | PLetIn of name * constr_pattern * constr_pattern
  | PSort of rawsort
  | PMeta of int option
  | PCase of constr_pattern option * constr_pattern * constr_pattern array
  | PFix of fixpoint
  | PCoFix of cofixpoint

let rec occur_meta_pattern = function
  | PApp (f,args) ->
      (occur_meta_pattern f) or (array_exists occur_meta_pattern args)
  | PLambda (na,t,c)  -> (occur_meta_pattern t) or (occur_meta_pattern c)
  | PProd (na,t,c)  -> (occur_meta_pattern t) or (occur_meta_pattern c)
  | PLetIn (na,t,c)  -> (occur_meta_pattern t) or (occur_meta_pattern c)
  | PCase(None,c,br)   ->
      (occur_meta_pattern c) or (array_exists occur_meta_pattern br)
  | PCase(Some p,c,br) ->
      (occur_meta_pattern p) or
      (occur_meta_pattern c) or (array_exists occur_meta_pattern br)
  | PMeta _ | PSoApp _ -> true
  | PEvar _ | PVar _ | PRef _ | PRel _ | PSort _ | PFix _ | PCoFix _ -> false

type constr_label =
  | ConstNode of constant
  | IndNode of inductive
  | CstrNode of constructor
  | VarNode of identifier

exception BoundPattern;;

let label_of_ref = function
  | ConstRef sp     -> ConstNode sp
  | IndRef sp       -> IndNode sp
  | ConstructRef sp -> CstrNode sp
  | VarRef id       -> VarNode id

let rec head_pattern_bound t =
  match t with
    | PProd (_,_,b)  -> head_pattern_bound b 
    | PLetIn (_,_,b) -> head_pattern_bound b 
    | PApp (c,args)  -> head_pattern_bound c
    | PCase (p,c,br) -> head_pattern_bound c
    | PRef r         -> label_of_ref r
    | PVar id        -> VarNode id
    | PEvar _ | PRel _ | PMeta _ | PSoApp _  | PSort _ | PFix _
	-> raise BoundPattern
    (* Perhaps they were arguments, but we don't beta-reduce *)
    | PLambda _ -> raise BoundPattern
    | PCoFix _ -> anomaly "head_pattern_bound: not a type"

let head_of_constr_reference c = match kind_of_term c with
  | Const sp -> ConstNode sp
  | Construct sp -> CstrNode sp
  | Ind sp -> IndNode sp
  | Var id -> VarNode id
  | _ -> anomaly "Not a rigid reference"


(* Second part : Given a term with second-order variables in it,
   represented by Meta's, and possibly applied using [SOAPP] to
   terms, this function will perform second-order, binding-preserving,
   matching, in the case where the pattern is a pattern in the sense
   of Dale Miller.

   ALGORITHM:

   Given a pattern, we decompose it, flattening Cast's and apply's,
   recursing on all operators, and pushing the name of the binder each
   time we descend a binder.

   When we reach a first-order variable, we ask that the corresponding
   term's free-rels all be higher than the depth of the current stack.

   When we reach a second-order application, we ask that the
   intersection of the free-rels of the term and the current stack be
   contained in the arguments of the application, and in that case, we
   construct a LAMBDA with the names on the stack.

 *)

exception PatternMatchingFailure

let constrain ((n : int),(m : constr)) sigma =
  if List.mem_assoc n sigma then
    if eq_constr m (List.assoc n sigma) then sigma
    else raise PatternMatchingFailure
  else 
    (n,m)::sigma
    
let build_lambda toabstract stk (m : constr) = 
  let rec buildrec m p_0 p_1 = match p_0,p_1 with 
    | (_, []) -> m
    | (n, (na,t)::tl) -> 
	if List.mem n toabstract then
          buildrec (mkLambda (na,t,m)) (n+1) tl
        else 
	  buildrec (pop m) (n+1) tl
  in 
  buildrec m 1 stk

let memb_metavars m n =
  match (m,n) with
    | (None, _)     -> true
    | (Some mvs, n) -> List.mem n mvs

let eq_context ctxt1 ctxt2 = array_for_all2 eq_constr ctxt1 ctxt2

let matches_core convert pat c = 
  let rec sorec stk sigma p t =
    let cT = strip_outer_cast t in
    match p,kind_of_term cT with
      | PSoApp (n,args),m ->
	  let relargs =
	    List.map
	      (function
		 | PRel n -> n
		 | _ -> error "Only bound indices are currently allowed in second order pattern matching")
	      args in
	  let frels = Intset.elements (free_rels cT) in
	  if list_subset frels relargs then
	    constrain (n,build_lambda relargs stk cT) sigma
	  else
	    raise PatternMatchingFailure

      | PMeta (Some n), m ->
	  let depth = List.length stk in
	  let frels = Intset.elements (free_rels cT) in
          if List.for_all (fun i -> i > depth) frels then
	    constrain (n,lift (-depth) cT) sigma
          else 
	    raise PatternMatchingFailure

      | PMeta None, m -> sigma

      | PRef (VarRef v1), Var v2 when v1 = v2 -> sigma

      | PVar v1, Var v2 when v1 = v2 -> sigma

      | PRef ref, _ when Declare.constr_of_reference ref = cT -> sigma

      | PRel n1, Rel n2 when n1 = n2 -> sigma

      | PSort (RProp c1), Sort (Prop c2) when c1 = c2 -> sigma

      | PSort (RType _), Sort (Type _) -> sigma

      | PApp (c1,arg1), App (c2,arg2) ->
        (try array_fold_left2 (sorec stk) (sorec stk sigma c1 c2) arg1 arg2
         with Invalid_argument _ -> raise PatternMatchingFailure)

      | PProd (na1,c1,d1), Prod(na2,c2,d2) ->
	  sorec ((na2,c2)::stk) (sorec stk sigma c1 c2) d1 d2

      | PLambda (na1,c1,d1), Lambda(na2,c2,d2) ->
	  sorec ((na2,c2)::stk) (sorec stk sigma c1 c2) d1 d2

      | PLetIn (na1,c1,d1), LetIn(na2,c2,t2,d2) ->
	  sorec ((na2,t2)::stk) (sorec stk sigma c1 c2) d1 d2

      | PRef (ConstRef _ as ref), _ when convert <> None ->
	  let (env,evars) = out_some convert in
	  let c = Declare.constr_of_reference ref in
	  if is_conv env evars c cT then sigma
	  else raise PatternMatchingFailure

      | PCase (_,a1,br1), Case (_,_,a2,br2) ->
	  (* On ne teste pas le prédicat *)
          if (Array.length br1) = (Array.length br2) then
  	    array_fold_left2 (sorec stk) (sorec stk sigma a1 a2) br1 br2
          else
            raise PatternMatchingFailure
      (* À faire *)
      |	PFix f0, Fix f1 when f0 = f1 -> sigma
      |	PCoFix c0, CoFix c1 when c0 = c1 -> sigma
      | _ -> raise PatternMatchingFailure

  in 
  Sort.list (fun (a,_) (b,_) -> a<b) (sorec [] [] pat c)

let matches = matches_core None

(* To skip to the next occurrence *)
exception NextOccurrence of int

(* Tells if it is an authorized occurrence *)
let authorized_occ nocc mres =
  if nocc = 0 then mres
  else raise (NextOccurrence nocc)

(* Tries matches according to the occurrence *)
let rec try_matches nocc pat = function
  | [] -> raise (NextOccurrence nocc)
  | c::tl ->
    (try authorized_occ nocc (matches pat c) with
    | PatternMatchingFailure -> (try_matches nocc pat tl)
    | NextOccurrence nocc -> (try_matches (nocc - 1) pat tl))

(* Tries to match a subterm of [c] with [pat] *)
let rec sub_match nocc pat c =
  match kind_of_term c with
  | Cast (c1,c2) ->
    (try authorized_occ nocc ((matches pat c), mkMeta (-1)) with
    | PatternMatchingFailure ->
      let (lm,lc) = try_sub_match nocc pat [c1] in
      (lm,mkCast (List.hd lc, c2))
    | NextOccurrence nocc ->
      let (lm,lc) = try_sub_match (nocc - 1) pat [c1] in
      (lm,mkCast (List.hd lc, c2)))
  | Lambda (x,c1,c2) ->
    (try authorized_occ nocc ((matches pat c), mkMeta (-1)) with
    | PatternMatchingFailure ->
      let (lm,lc) = try_sub_match nocc pat [c1;c2] in
      (lm,mkLambda (x,List.hd lc,List.nth lc 1))
    | NextOccurrence nocc ->
      let (lm,lc) = try_sub_match (nocc - 1) pat [c1;c2] in
      (lm,mkLambda (x,List.hd lc,List.nth lc 1)))
  | Prod (x,c1,c2) ->
    (try authorized_occ nocc ((matches pat c), mkMeta (-1)) with
    | PatternMatchingFailure ->
      let (lm,lc) = try_sub_match nocc pat [c1;c2] in
      (lm,mkProd (x,List.hd lc,List.nth lc 1))
    | NextOccurrence nocc ->
      let (lm,lc) = try_sub_match (nocc - 1) pat [c1;c2] in
      (lm,mkProd (x,List.hd lc,List.nth lc 1)))
  | LetIn (x,c1,t2,c2) ->
    (try authorized_occ nocc ((matches pat c), mkMeta (-1)) with
    | PatternMatchingFailure ->
      let (lm,lc) = try_sub_match nocc pat [c1;t2;c2] in
      (lm,mkLetIn (x,List.hd lc,List.nth lc 1,List.nth lc 2))
    | NextOccurrence nocc ->
      let (lm,lc) = try_sub_match (nocc - 1) pat [c1;t2;c2] in
      (lm,mkLetIn (x,List.hd lc,List.nth lc 1,List.nth lc 2)))
  | App (c1,lc) ->
    (try authorized_occ nocc ((matches pat c), mkMeta (-1)) with
    | PatternMatchingFailure ->
      let (lm,le) = try_sub_match nocc pat (c1::(Array.to_list lc)) in
      (lm,mkApp (List.hd le, Array.of_list (List.tl le)))
    | NextOccurrence nocc ->
      let (lm,le) = try_sub_match (nocc - 1) pat (c1::(Array.to_list lc)) in
      (lm,mkApp (List.hd le, Array.of_list (List.tl le))))
  | Case (ci,hd,c1,lc) ->
    (try authorized_occ nocc ((matches pat c), mkMeta (-1)) with
    | PatternMatchingFailure ->
      let (lm,le) = try_sub_match nocc pat (c1::Array.to_list lc) in
      (lm,mkCase (ci,hd,List.hd le,Array.of_list (List.tl le)))
    | NextOccurrence nocc ->
      let (lm,le) = try_sub_match (nocc - 1) pat (c1::Array.to_list lc) in
      (lm,mkCase (ci,hd,List.hd le,Array.of_list (List.tl le))))
  | Construct _ | Fix _ | Ind _|CoFix _ |Evar _|Const _
  | Rel _|Meta _|Var _|Sort _ ->
    (try authorized_occ nocc ((matches pat c),mkMeta (-1)) with
    | PatternMatchingFailure -> raise (NextOccurrence nocc)
    | NextOccurrence nocc -> raise (NextOccurrence (nocc - 1)))

(* Tries [sub_match] for all terms in the list *)
and try_sub_match nocc pat lc =
  let rec try_sub_match_rec nocc pat lacc = function
    | [] -> raise (NextOccurrence nocc)
    | c::tl ->
      (try 
         let (lm,ce) = sub_match nocc pat c in
         (lm,lacc@(ce::tl))
       with
      | NextOccurrence nocc -> try_sub_match_rec nocc pat (lacc@[c]) tl) in
  try_sub_match_rec nocc pat [] lc

let is_matching pat n =
  try let _ = matches pat n in true
  with PatternMatchingFailure -> false

let matches_conv env sigma = matches_core (Some (env,sigma))

let is_matching_conv env sigma pat n =
  try let _ = matches_conv env sigma pat n in true
  with PatternMatchingFailure -> false

let rec pattern_of_constr t =
  match kind_of_term t with
    | Rel n  -> PRel n
    | Meta n -> PMeta (Some n)
    | Var id -> PVar id
    | Sort (Prop c) -> PSort (RProp c)
    | Sort (Type _) -> PSort (RType None)
    | Cast (c,_)      -> pattern_of_constr c
    | LetIn (na,c,_,b) -> PLetIn (na,pattern_of_constr c,pattern_of_constr b)
    | Prod (na,c,b)   -> PProd (na,pattern_of_constr c,pattern_of_constr b)
    | Lambda (na,c,b) -> PLambda (na,pattern_of_constr c,pattern_of_constr b)
    | App (f,a) -> PApp (pattern_of_constr f,Array.map pattern_of_constr a)
    | Const sp         -> PRef (ConstRef sp)
    | Ind sp        -> PRef (IndRef sp)
    | Construct sp -> PRef (ConstructRef sp)
    | Evar (n,ctxt) ->
	if ctxt = [||] then PEvar n
	else PApp (PEvar n, Array.map pattern_of_constr ctxt)
    | Case (ci,p,a,br) ->
	PCase (Some (pattern_of_constr p),pattern_of_constr a,
	       Array.map pattern_of_constr br)
    | Fix f -> PFix f
    | CoFix _ ->
	error "pattern_of_constr: (co)fix currently not supported"