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(* Copyright (c) 2008, Adam Chlipala
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* - Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* - The names of contributors may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*)
(* Simplify a Mono program algebraically *)
structure MonoReduce :> MONO_REDUCE = struct
open Mono
structure E = MonoEnv
structure U = MonoUtil
fun impure (e, _) =
case e of
EWrite _ => true
| EQuery _ => true
| EAbs _ => false
| EPrim _ => false
| ERel _ => false
| ENamed _ => false
| ECon (_, _, eo) => (case eo of NONE => false | SOME e => impure e)
| ESome (_, e) => impure e
| EFfi _ => false
| EFfiApp _ => false
| EApp ((EFfi _, _), _) => false
| EApp _ => true
| ERecord xes => List.exists (fn (_, e, _) => impure e) xes
| EField (e, _) => impure e
| ECase (e, pes, _) => impure e orelse List.exists (fn (_, e) => impure e) pes
| EError (e, _) => impure e
| EStrcat (e1, e2) => impure e1 orelse impure e2
| ESeq (e1, e2) => impure e1 orelse impure e2
| ELet (_, _, e1, e2) => impure e1 orelse impure e2
| EClosure (_, es) => List.exists impure es
val liftExpInExp = Monoize.liftExpInExp
val subExpInExp' =
U.Exp.mapB {typ = fn t => t,
exp = fn (xn, rep) => fn e =>
case e of
ERel xn' =>
(case Int.compare (xn', xn) of
EQUAL => #1 rep
| GREATER=> ERel (xn' - 1)
| LESS => e)
| _ => e,
bind = fn ((xn, rep), U.Exp.RelE _) => (xn+1, liftExpInExp 0 rep)
| (ctx, _) => ctx}
fun subExpInExp (n, e1) e2 =
let
val r = subExpInExp' (n, e1) e2
in
(*Print.prefaces "subExpInExp" [("e1", MonoPrint.p_exp MonoEnv.empty e1),
("e2", MonoPrint.p_exp MonoEnv.empty e2),
("r", MonoPrint.p_exp MonoEnv.empty r)];*)
r
end
fun typ c = c
datatype result = Yes of E.env | No | Maybe
fun match (env, p : pat, e : exp) =
case (#1 p, #1 e) of
(PWild, _) => Yes env
| (PVar (x, t), _) => Yes (E.pushERel env x t (SOME e))
| (PPrim (Prim.String s), EStrcat ((EPrim (Prim.String s'), _), _)) =>
if String.isPrefix s' s then
Maybe
else
No
| (PPrim p, EPrim p') =>
if Prim.equal (p, p') then
Yes env
else
No
| (PCon (_, PConVar n1, NONE), ECon (_, PConVar n2, NONE)) =>
if n1 = n2 then
Yes env
else
No
| (PCon (_, PConVar n1, SOME p), ECon (_, PConVar n2, SOME e)) =>
if n1 = n2 then
match (env, p, e)
else
No
| (PCon (_, PConFfi {mod = m1, con = con1, ...}, NONE), ECon (_, PConFfi {mod = m2, con = con2, ...}, NONE)) =>
if m1 = m2 andalso con1 = con2 then
Yes env
else
No
| (PCon (_, PConFfi {mod = m1, con = con1, ...}, SOME ep), ECon (_, PConFfi {mod = m2, con = con2, ...}, SOME e)) =>
if m1 = m2 andalso con1 = con2 then
match (env, p, e)
else
No
| (PRecord xps, ERecord xes) =>
let
fun consider (xps, env) =
case xps of
[] => Yes env
| (x, p, _) :: rest =>
case List.find (fn (x', _, _) => x' = x) xes of
NONE => No
| SOME (_, e, _) =>
case match (env, p, e) of
No => No
| Maybe => Maybe
| Yes env => consider (rest, env)
in
consider (xps, env)
end
| _ => Maybe
fun exp env e =
case e of
ERel n =>
(case E.lookupERel env n of
(_, _, SOME e') => #1 e'
| _ => e)
| ENamed n =>
(case E.lookupENamed env n of
(_, _, SOME e', _) => #1 e'
| _ => e)
| EApp ((EAbs (x, t, _, e1), loc), e2) =>
((*Print.prefaces "Considering" [("e1", MonoPrint.p_exp env e1),
("e2", MonoPrint.p_exp env e2)];*)
if impure e2 then
#1 (reduceExp env (ELet (x, t, e2, e1), loc))
else
#1 (reduceExp env (subExpInExp (0, e2) e1)))
| ECase (disc, pes, _) =>
let
fun search pes =
case pes of
[] => e
| (p, body) :: pes =>
case match (env, p, disc) of
No => search pes
| Maybe => e
| Yes env => #1 (reduceExp env body)
in
search pes
end
| EField ((ERecord xes, _), x) =>
(case List.find (fn (x', _, _) => x' = x) xes of
SOME (_, e, _) => #1 e
| NONE => e)
| ELet (x1, t1, (ELet (x2, t2, e1, b1), loc), b2) =>
let
val e' = (ELet (x2, t2, e1,
(ELet (x1, t1, b1,
liftExpInExp 1 b2), loc)), loc)
in
(*Print.prefaces "ELet commute" [("e", MonoPrint.p_exp env (e, loc)),
("e'", MonoPrint.p_exp env e')];*)
#1 (reduceExp env e')
end
| EApp ((ELet (x, t, e, b), loc), e') =>
#1 (reduceExp env (ELet (x, t, e,
(EApp (b, liftExpInExp 0 e'), loc)), loc))
| ELet (x, t, e', b) =>
if impure e' then
e
else
#1 (reduceExp env (subExpInExp (0, e') b))
| EStrcat ((EPrim (Prim.String s1), _), (EPrim (Prim.String s2), _)) =>
EPrim (Prim.String (s1 ^ s2))
| _ => e
and bind (env, b) =
case b of
U.Decl.Datatype (x, n, xncs) => E.pushDatatype env x n xncs
| U.Decl.RelE (x, t) => E.pushERel env x t NONE
| U.Decl.NamedE (x, n, t, eo, s) => E.pushENamed env x n t (Option.map (reduceExp env) eo) s
and reduceExp env = U.Exp.mapB {typ = typ, exp = exp, bind = bind} env
fun decl env d = d
val reduce = U.File.mapB {typ = typ, exp = exp, decl = decl, bind = bind} E.empty
end
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