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Beta reductions for expressions
author Adam Chlipala <adamc@hcoop.net>
date Sun, 08 Jun 2008 16:02:26 -0400
parents 1ab48e37d0ef
children d8850cc06d24
rev   line source
adamc@20 1 (* Copyright (c) 2008, Adam Chlipala
adamc@20 2 * All rights reserved.
adamc@20 3 *
adamc@20 4 * Redistribution and use in source and binary forms, with or without
adamc@20 5 * modification, are permitted provided that the following conditions are met:
adamc@20 6 *
adamc@20 7 * - Redistributions of source code must retain the above copyright notice,
adamc@20 8 * this list of conditions and the following disclaimer.
adamc@20 9 * - Redistributions in binary form must reproduce the above copyright notice,
adamc@20 10 * this list of conditions and the following disclaimer in the documentation
adamc@20 11 * and/or other materials provided with the distribution.
adamc@20 12 * - The names of contributors may not be used to endorse or promote products
adamc@20 13 * derived from this software without specific prior written permission.
adamc@20 14 *
adamc@20 15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
adamc@20 16 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
adamc@20 17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
adamc@20 18 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
adamc@20 19 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
adamc@20 20 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
adamc@20 21 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
adamc@20 22 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
adamc@20 23 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
adamc@20 24 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
adamc@20 25 * POSSIBILITY OF SUCH DAMAGE.
adamc@20 26 *)
adamc@20 27
adamc@20 28 (* Simplify a Core program algebraically *)
adamc@20 29
adamc@20 30 structure Reduce :> REDUCE = struct
adamc@20 31
adamc@20 32 open Core
adamc@20 33
adamc@20 34 structure E = CoreEnv
adamc@20 35 structure U = CoreUtil
adamc@20 36
adamc@20 37 val liftConInCon = E.liftConInCon
adamc@20 38
adamc@20 39 val subConInCon =
adamc@20 40 U.Con.mapB {kind = fn k => k,
adamc@20 41 con = fn (xn, rep) => fn c =>
adamc@20 42 case c of
adamc@20 43 CRel xn' =>
adamc@20 44 if xn = xn' then
adamc@20 45 #1 rep
adamc@20 46 else
adamc@20 47 c
adamc@20 48 | _ => c,
adamc@20 49 bind = fn ((xn, rep), U.Con.Rel _) => (xn+1, liftConInCon 0 rep)
adamc@20 50 | (ctx, _) => ctx}
adamc@20 51
adamc@21 52 val liftExpInExp =
adamc@21 53 U.Exp.mapB {kind = fn k => k,
adamc@21 54 con = fn _ => fn c => c,
adamc@21 55 exp = fn bound => fn e =>
adamc@21 56 case e of
adamc@21 57 ERel xn =>
adamc@21 58 if xn < bound then
adamc@21 59 e
adamc@21 60 else
adamc@21 61 ERel (xn + 1)
adamc@21 62 | _ => e,
adamc@21 63 bind = fn (bound, U.Exp.RelE _) => bound + 1
adamc@21 64 | (bound, _) => bound}
adamc@21 65
adamc@21 66 val subExpInExp =
adamc@21 67 U.Exp.mapB {kind = fn k => k,
adamc@21 68 con = fn _ => fn c => c,
adamc@21 69 exp = fn (xn, rep) => fn e =>
adamc@21 70 case e of
adamc@21 71 ERel xn' =>
adamc@21 72 if xn = xn' then
adamc@21 73 #1 rep
adamc@21 74 else
adamc@21 75 e
adamc@21 76 | _ => e,
adamc@21 77 bind = fn ((xn, rep), U.Exp.RelE _) => (xn+1, liftExpInExp 0 rep)
adamc@21 78 | (ctx, _) => ctx}
adamc@21 79
adamc@21 80 val liftConInExp =
adamc@21 81 U.Exp.mapB {kind = fn k => k,
adamc@21 82 con = fn bound => fn c =>
adamc@21 83 case c of
adamc@21 84 CRel xn =>
adamc@21 85 if xn < bound then
adamc@21 86 c
adamc@21 87 else
adamc@21 88 CRel (xn + 1)
adamc@21 89 | _ => c,
adamc@21 90 exp = fn _ => fn e => e,
adamc@21 91 bind = fn (bound, U.Exp.RelC _) => bound + 1
adamc@21 92 | (bound, _) => bound}
adamc@21 93
adamc@21 94 val subConInExp =
adamc@21 95 U.Exp.mapB {kind = fn k => k,
adamc@21 96 con = fn (xn, rep) => fn c =>
adamc@21 97 case c of
adamc@21 98 CRel xn' =>
adamc@21 99 if xn = xn' then
adamc@21 100 #1 rep
adamc@21 101 else
adamc@21 102 c
adamc@21 103 | _ => c,
adamc@21 104 exp = fn _ => fn e => e,
adamc@21 105 bind = fn ((xn, rep), U.Exp.RelC _) => (xn+1, liftConInCon 0 rep)
adamc@21 106 | (ctx, _) => ctx}
adamc@21 107
adamc@20 108 fun bindC (env, b) =
adamc@20 109 case b of
adamc@20 110 U.Con.Rel (x, k) => E.pushCRel env x k
adamc@20 111 | U.Con.Named (x, n, k, co) => E.pushCNamed env x n k co
adamc@20 112
adamc@20 113 fun bind (env, b) =
adamc@20 114 case b of
adamc@20 115 U.Decl.RelC (x, k) => E.pushCRel env x k
adamc@20 116 | U.Decl.NamedC (x, n, k, co) => E.pushCNamed env x n k co
adamc@20 117 | U.Decl.RelE (x, t) => E.pushERel env x t
adamc@20 118 | U.Decl.NamedE (x, n, t, eo) => E.pushENamed env x n t eo
adamc@20 119
adamc@20 120 fun kind k = k
adamc@20 121
adamc@20 122 fun con env c =
adamc@20 123 case c of
adamc@20 124 CApp ((CAbs (_, _, c1), loc), c2) =>
adamc@20 125 #1 (reduceCon env (subConInCon (0, c2) c1))
adamc@20 126 | CNamed n =>
adamc@20 127 (case E.lookupCNamed env n of
adamc@20 128 (_, _, SOME c') => #1 c'
adamc@20 129 | _ => c)
adamc@20 130 | CConcat ((CRecord (k, xcs1), loc), (CRecord (_, xcs2), _)) => CRecord (k, xcs1 @ xcs2)
adamc@20 131 | _ => c
adamc@20 132
adamc@20 133 and reduceCon env = U.Con.mapB {kind = kind, con = con, bind = bindC} env
adamc@20 134
adamc@21 135 fun exp env e =
adamc@21 136 case e of
adamc@21 137 ENamed n =>
adamc@21 138 (case E.lookupENamed env n of
adamc@21 139 (_, _, SOME e') => #1 e'
adamc@21 140 | _ => e)
adamc@21 141
adamc@21 142 | EApp ((EAbs (_, _, e1), loc), e2) =>
adamc@21 143 #1 (reduceExp env (subExpInExp (0, e2) e1))
adamc@21 144 | ECApp ((ECAbs (_, _, e1), loc), c) =>
adamc@21 145 #1 (reduceExp env (subConInExp (0, c) e1))
adamc@21 146
adamc@21 147 | _ => e
adamc@21 148
adamc@21 149 and reduceExp env = U.Exp.mapB {kind = kind, con = con, exp = exp, bind = bind} env
adamc@20 150
adamc@20 151 fun decl env d = d
adamc@20 152
adamc@20 153 val reduce = U.File.mapB {kind = kind, con = con, exp = exp, decl = decl, bind = bind} CoreEnv.basis
adamc@20 154
adamc@20 155 end