(************************************************************************)
(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
(* <O___,, * CNRS-Ecole Polytechnique-INRIA Futurs-Universite Paris Sud *)
(*   \VV/  **************************************************************)
(*    //   *      This file is distributed under the terms of the       *)
(*         *       GNU Lesser General Public License Version 2.1        *)
(************************************************************************)

(* $Id: redexpr.ml 7639 2005-12-02 10:01:15Z gregoire $ *)

open Pp
open Util
open Names
open Term
open Declarations
open Libnames
open Rawterm
open Reductionops
open Tacred
open Closure
open RedFlags


(* call by value normalisation function using the virtual machine *)
let cbv_vm env _ c =
  let ctyp = (fst (Typeops.infer env c)).Environ.uj_type in
  Vconv.cbv_vm env c ctyp


let set_opaque_const sp = 
  Conv_oracle.set_opaque_const sp;
  Csymtable.set_opaque_const sp

let set_transparent_const sp =
  let cb = Global.lookup_constant sp in
  if cb.const_body <> None & cb.const_opaque then
    errorlabstrm "set_transparent_const"
      (str "Cannot make" ++ spc () ++ 
         Nametab.pr_global_env Idset.empty (ConstRef sp) ++
         spc () ++ str "transparent because it was declared opaque.");
  Conv_oracle.set_transparent_const sp;
  Csymtable.set_transparent_const sp

let set_opaque_var      = Conv_oracle.set_opaque_var
let set_transparent_var = Conv_oracle.set_transparent_var

let _ = 
  Summary.declare_summary "Transparent constants and variables"
    { Summary.freeze_function = Conv_oracle.freeze;
      Summary.unfreeze_function = Conv_oracle.unfreeze;
      Summary.init_function = Conv_oracle.init;
      Summary.survive_module = false;
      Summary.survive_section = false }


(* Generic reduction: reduction functions used in reduction tactics *)

type red_expr = (constr, evaluable_global_reference) red_expr_gen


let make_flag_constant = function
  | EvalVarRef id -> fVAR id
  | EvalConstRef sp -> fCONST sp

let make_flag f =
  let red = no_red in
  let red = if f.rBeta then red_add red fBETA else red in
  let red = if f.rIota then red_add red fIOTA else red in
  let red = if f.rZeta then red_add red fZETA else red in
  let red =
    if f.rDelta then (* All but rConst *)
        let red = red_add red fDELTA in
        let red = red_add_transparent red (Conv_oracle.freeze ()) in
	List.fold_right
	  (fun v red -> red_sub red (make_flag_constant v))
	  f.rConst red
    else (* Only rConst *)
        let red = red_add_transparent (red_add red fDELTA) all_opaque in
	List.fold_right
	  (fun v red -> red_add red (make_flag_constant v))
	  f.rConst red
  in red

let is_reference c = 
  try let _ref = global_of_constr c in true with _ -> false

let red_expr_tab = ref Stringmap.empty

let declare_red_expr s f =
  try 
    let _ = Stringmap.find s !red_expr_tab in
    error ("There is already a reduction expression of name "^s)
  with Not_found ->
    red_expr_tab := Stringmap.add s f !red_expr_tab

let reduction_of_red_expr = function
  | Red internal -> 
      if internal then (try_red_product,DEFAULTcast) 
      else (red_product,DEFAULTcast)
  | Hnf -> (hnf_constr,DEFAULTcast)
  | Simpl (Some (_,c as lp)) -> 
      (contextually (is_reference c) lp nf,DEFAULTcast)
  | Simpl None -> (nf,DEFAULTcast)
  | Cbv f -> (cbv_norm_flags (make_flag f),DEFAULTcast)
  | Lazy f -> (clos_norm_flags (make_flag f),DEFAULTcast)
  | Unfold ubinds -> (unfoldn ubinds,DEFAULTcast)
  | Fold cl -> (fold_commands cl,DEFAULTcast)
  | Pattern lp -> (pattern_occs lp,DEFAULTcast)
  | ExtraRedExpr s ->
      (try (Stringmap.find s !red_expr_tab,DEFAULTcast)
      with Not_found -> error("unknown user-defined reduction \""^s^"\""))
  | CbvVm -> (cbv_vm ,VMcast)