adamc@133: (* Copyright (c) 2008, Adam Chlipala
adamc@133:  * All rights reserved.
adamc@133:  *
adamc@133:  * Redistribution and use in source and binary forms, with or without
adamc@133:  * modification, are permitted provided that the following conditions are met:
adamc@133:  *
adamc@133:  * - Redistributions of source code must retain the above copyright notice,
adamc@133:  *   this list of conditions and the following disclaimer.
adamc@133:  * - Redistributions in binary form must reproduce the above copyright notice,
adamc@133:  *   this list of conditions and the following disclaimer in the documentation
adamc@133:  *   and/or other materials provided with the distribution.
adamc@133:  * - The names of contributors may not be used to endorse or promote products
adamc@133:  *   derived from this software without specific prior written permission.
adamc@133:  *
adamc@133:  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
adamc@133:  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
adamc@133:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
adamc@133:  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
adamc@133:  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
adamc@133:  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
adamc@133:  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
adamc@133:  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
adamc@133:  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
adamc@133:  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
adamc@133:  * POSSIBILITY OF SUCH DAMAGE.
adamc@133:  *)
adamc@133: 
adamc@133: (* Simplify a Mono program algebraically *)
adamc@133: 
adamc@133: structure MonoReduce :> MONO_REDUCE = struct
adamc@133: 
adamc@133: open Mono
adamc@133: 
adamc@133: structure E = MonoEnv
adamc@133: structure U = MonoUtil
adamc@133: 
adamc@133: val liftExpInExp =
adamc@133:     U.Exp.mapB {typ = fn t => t,
adamc@133:                 exp = fn bound => fn e =>
adamc@133:                                      case e of
adamc@133:                                          ERel xn =>
adamc@133:                                          if xn < bound then
adamc@133:                                              e
adamc@133:                                          else
adamc@133:                                              ERel (xn + 1)
adamc@133:                                        | _ => e,
adamc@133:                 bind = fn (bound, U.Exp.RelE _) => bound + 1
adamc@133:                         | (bound, _) => bound}
adamc@133: 
adamc@133: val subExpInExp =
adamc@133:     U.Exp.mapB {typ = fn t => t,
adamc@133:                 exp = fn (xn, rep) => fn e =>
adamc@133:                                   case e of
adamc@133:                                       ERel xn' =>
adamc@133:                                       (case Int.compare (xn', xn) of
adamc@133:                                            EQUAL => #1 rep
adamc@133:                                          | GREATER=> ERel (xn' - 1)
adamc@133:                                          | LESS => e)
adamc@133:                                     | _ => e,
adamc@133:                 bind = fn ((xn, rep), U.Exp.RelE _) => (xn+1, liftExpInExp 0 rep)
adamc@133:                         | (ctx, _) => ctx}
adamc@133: 
adamc@133: fun bind (env, b) =
adamc@133:     case b of
adamc@168:         U.Decl.Datatype (x, n, xncs) => E.pushDatatype env x n xncs
adamc@183:       | U.Decl.RelE (x, t) => E.pushERel env x t NONE
adamc@133:       | U.Decl.NamedE (x, n, t, eo, s) => E.pushENamed env x n t eo s
adamc@133: 
adamc@133: fun typ c = c
adamc@133: 
adamc@183: fun match (env, p : pat, e : exp) =
adamc@183:     case (#1 p, #1 e) of
adamc@183:         (PWild, _) => SOME env
adamc@183:       | (PVar (x, t), _) => SOME (E.pushERel env x t (SOME e))
adamc@183: 
adamc@183:       | (PPrim p, EPrim p') =>
adamc@183:         if Prim.equal (p, p') then
adamc@183:             SOME env
adamc@183:         else
adamc@183:             NONE
adamc@183: 
adamc@183:       | (PCon (PConVar n1, NONE), ECon (n2, NONE)) =>
adamc@183:         if n1 = n2 then
adamc@183:             SOME env
adamc@183:         else
adamc@183:             NONE
adamc@183: 
adamc@183:       | (PCon (PConVar n1, SOME p), ECon (n2, SOME e)) =>
adamc@183:         if n1 = n2 then
adamc@183:             match (env, p, e)
adamc@183:         else
adamc@183:             NONE
adamc@183: 
adamc@183:       | (PRecord xps, ERecord xes) =>
adamc@183:         let
adamc@183:             fun consider (xps, env) =
adamc@183:                 case xps of
adamc@183:                     [] => SOME env
adamc@183:                   | (x, p, _) :: rest =>
adamc@183:                     case List.find (fn (x', _, _) => x' = x) xes of
adamc@183:                         NONE => NONE
adamc@183:                       | SOME (_, e, _) =>
adamc@183:                         case match (env, p, e) of
adamc@183:                             NONE => NONE
adamc@183:                           | SOME env => consider (rest, env)
adamc@183:         in
adamc@183:             consider (xps, env)
adamc@183:         end
adamc@183: 
adamc@183:       | _ => NONE
adamc@183: 
adamc@133: fun exp env e =
adamc@133:     case e of
adamc@183:         ERel n =>
adamc@183:         (case E.lookupERel env n of
adamc@183:              (_, _, SOME e') => #1 e'
adamc@183:            | _ => e)
adamc@183:       | ENamed n =>
adamc@133:         (case E.lookupENamed env n of
adamc@133:              (_, _, SOME e', _) => #1 e'
adamc@133:            | _ => e)
adamc@133: 
adamc@133:       | EApp ((EAbs (_, _, _, e1), loc), e2) =>
adamc@133:         #1 (reduceExp env (subExpInExp (0, e2) e1))
adamc@133: 
adamc@183:       | ECase (disc, pes, t) =>
adamc@183:         (case ListUtil.search (fn (p, body) =>
adamc@183:                                   case match (env, p, disc) of
adamc@183:                                       NONE => NONE
adamc@183:                                     | SOME env => SOME (#1 (reduceExp env body))) pes of
adamc@183:              NONE => e
adamc@183:            | SOME e' => e')
adamc@183: 
adamc@133:       | _ => e
adamc@133: 
adamc@133: and reduceExp env = U.Exp.mapB {typ = typ, exp = exp, bind = bind} env
adamc@133: 
adamc@133: fun decl env d = d
adamc@133: 
adamc@133: val reduce = U.File.mapB {typ = typ, exp = exp, decl = decl, bind = bind} E.empty
adamc@133: 
adamc@133: end