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1 | (* HCoop Domtool (http://hcoop.sourceforge.net/) |
2 | * Copyright (c) 2006, Adam Chlipala | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or | |
5 | * modify it under the terms of the GNU General Public License | |
6 | * as published by the Free Software Foundation; either version 2 | |
7 | * of the License, or (at your option) any later version. | |
8 | * | |
9 | * This program is distributed in the hope that it will be useful, | |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
12 | * GNU General Public License for more details. | |
13 | * | |
14 | * You should have received a copy of the GNU General Public License | |
15 | * along with this program; if not, write to the Free Software | |
16 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. | |
dac62e84 | 17 | *) |
492c1cff AC |
18 | |
19 | (* Evaluation of expressions until only externs are around *) | |
20 | ||
21 | structure Reduce :> REDUCE = struct | |
22 | ||
23 | open Ast Print Env | |
24 | ||
25 | fun freeIn x (b, _) = | |
26 | case b of | |
27 | EInt _ => false | |
28 | | EString _ => false | |
29 | | EList es => List.exists (freeIn x) es | |
30 | ||
31 | | ELam (x', _, b') => x <> x' andalso freeIn x b' | |
32 | | EVar x' => x = x' | |
33 | | EApp (e1, e2) => freeIn x e1 orelse freeIn x e2 | |
34 | ||
35 | | ESkip => false | |
36 | | ESet (_, e) => freeIn x e | |
37 | | EGet (x', _, b') => x <> x' andalso freeIn x b' | |
38 | | ESeq es => List.exists (freeIn x) es | |
39 | | ELocal (e1, e2) => freeIn x e1 orelse freeIn x e2 | |
40 | | EWith (e1, e2) => freeIn x e1 orelse freeIn x e2 | |
41 | ||
42 | local | |
43 | val freshCount = ref 0 | |
44 | in | |
45 | fun freshVar () = | |
46 | let | |
47 | val v = !freshCount | |
48 | in | |
49 | freshCount := v + 1; | |
50 | Int.toString v ^ "v" | |
51 | end | |
52 | end | |
53 | ||
54 | fun subst x e (bAll as (b, loc)) = | |
55 | case b of | |
56 | EInt _ => bAll | |
57 | | EString _ => bAll | |
58 | | EList es => (EList (map (subst x e) es), loc) | |
59 | ||
60 | | ELam (x', to, b') => | |
61 | if x = x' then | |
62 | bAll | |
63 | else if freeIn x' e then | |
64 | let | |
65 | val x'' = freshVar () | |
66 | in | |
67 | (ELam (x'', to, subst x e (subst x' (EVar x'', loc) b')), loc) | |
68 | end | |
69 | else | |
70 | (ELam (x', to, subst x e b'), loc) | |
71 | | EVar x' => | |
72 | if x = x' then | |
73 | e | |
74 | else | |
75 | bAll | |
76 | | EApp (b1, b2) => (EApp (subst x e b1, subst x e b2), loc) | |
77 | ||
78 | | ESkip => bAll | |
79 | | ESet (v, b) => (ESet (v, subst x e b), loc) | |
80 | | EGet (x', v, b') => | |
81 | if x = x' then | |
82 | bAll | |
83 | else if freeIn x' e then | |
84 | let | |
85 | val x'' = freshVar () | |
86 | in | |
87 | (EGet (x'', v, subst x e (subst x' (EVar x'', loc) b')), loc) | |
88 | end | |
89 | else | |
90 | (EGet (x', v, subst x e b'), loc) | |
91 | | ESeq es => (ESeq (map (subst x e) es), loc) | |
92 | | ELocal (b1, b2) => (ELocal (subst x e b1, subst x e b2), loc) | |
93 | | EWith (b1, b2) => (EWith (subst x e b1, subst x e b2), loc) | |
94 | ||
95 | fun reduceExp G (eAll as (e, loc)) = | |
96 | case e of | |
97 | EInt _ => eAll | |
98 | | EString _ => eAll | |
99 | | EList es => (EList (map (reduceExp G) es), loc) | |
100 | ||
101 | | ELam (x, to, e) => | |
102 | let | |
103 | val to' = case to of | |
104 | NONE => (Tycheck.newUnif (), loc) | |
105 | | SOME to => to | |
106 | ||
107 | val G' = bindVal G (x, to', NONE) | |
108 | in | |
109 | (ELam (x, to, reduceExp G' e), loc) | |
110 | end | |
111 | | EVar x => | |
112 | (case lookupEquation G x of | |
113 | NONE => eAll | |
114 | | SOME e => reduceExp G e) | |
115 | | EApp (e1, e2) => | |
116 | let | |
117 | val e1' = reduceExp G e1 | |
118 | val e2' = reduceExp G e2 | |
119 | in | |
120 | case e1' of | |
121 | (ELam (x, _, b), _) => reduceExp G (subst x e2' b) | |
122 | | _ => (EApp (e1', e2'), loc) | |
123 | end | |
124 | ||
125 | | ESkip => eAll | |
126 | | ESet (v, b) => (ESet (v, reduceExp G b), loc) | |
127 | | EGet (x, v, b) => (EGet (x, v, reduceExp G b), loc) | |
128 | | ESeq es => (ESeq (map (reduceExp G) es), loc) | |
129 | | ELocal (e1, e2) => (ELocal (reduceExp G e1, reduceExp G e2), loc) | |
130 | | EWith (e1, e2) => (EWith (reduceExp G e1, reduceExp G e2), loc) | |
131 | ||
132 | end |