Create exp2eq.ml

A pass to simplify the language
of expressions. It rewrites :
- Ematch into EQmatch;
- Ereset into EQreset.

src/compiler/rewrite/exp2eq.ml

@@ -0,0 +1,64 @@
+(***********************************************************************)
+(*                                                                     *)
+(*                                                                     *)
+(*          Zelus, a synchronous language for hybrid systems           *)
+(*                                                                     *)
+(*  (c) 2024 Inria Paris (see the AUTHORS file)                        *)
+(*                                                                     *)
+(*  Copyright Institut National de Recherche en Informatique et en     *)
+(*  Automatique. All rights reserved. This file is distributed under   *)
+(*  the terms of the INRIA Non-Commercial License Agreement (see the   *)
+(*  LICENSE file).                                                     *)
+(*                                                                     *)
+(* *********************************************************************)
+
+(* translate some expressions into equations *)
+(* the constructs that are concerned are:
+ *- [match e with P1 -> e1 | ... | Pn -> en] =>
+    [let match e with P1 -> r = e1 | ... | Pn -> r = en in r]
+*- [reset e every c] => let reset r = e every c in r]
+*)
+
+open Misc
+open Location
+open Ident
+open Zelus
+open Mapfold
+
+let empty = ()
+
+let fresh () = Ident.fresh "r"
+
+let expression funs acc e = 
+  let ({ e_desc; e_loc } as e), acc = Mapfold.expression funs acc e in
+  match e_desc with
+  | Ematch { is_total; e; handlers } ->
+     let result = fresh () in
+     let handler { m_pat; m_body; m_env; m_loc; m_reset; m_zero } =
+       { m_pat; m_body = Aux.id_eq result m_body; m_env; m_loc; m_reset; m_zero } in
+     let eq =
+       { eq_desc = EQmatch { is_total; e; handlers = List.map handler handlers };
+         eq_write = Defnames.singleton result;
+         eq_safe = true; eq_index = -1; eq_loc = e_loc } in
+     Aux.e_let (Aux.leq [eq]) (Aux.var result), acc
+  | Ereset(e, e_r) ->
+     let result = fresh () in
+     let eq =
+       { eq_desc = EQreset(Aux.id_eq result e, e_r);
+         eq_write = Defnames.singleton result;
+         eq_safe = true; eq_index = -1; eq_loc = e_loc } in
+     Aux.e_let (Aux.leq [eq]) (Aux.var result), acc
+     | _ -> e, acc
+
+let set_index funs acc n =
+  let _ = Ident.set n in n, acc
+let get_index funs acc n = Ident.get (), acc
+
+let program _ p =
+  let global_funs = Mapfold.default_global_funs in
+  let funs =
+    { Mapfold.defaults with expression; set_index; get_index; global_funs } in
+  let { p_impl_list } as p, _ =
+    Mapfold.program_it funs empty p in
+  { p with p_impl_list = p_impl_list }
+