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[diderot] Annotation of /trunk/src/compiler/typechecker/util.sml
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Annotation of /trunk/src/compiler/typechecker/util.sml

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1 : jhr 80 (* util.sml
2 :     *
3 :     * COPYRIGHT (c) 2010 The Diderot Project (http://diderot.cs.uchicago.edu)
4 :     * All rights reserved.
5 :     *
6 :     * Utilities for typechecking
7 :     *)
8 :    
9 : jhr 85 structure Util : sig
10 : jhr 80
11 : jhr 85 val matchType : Types.ty * Types.ty -> bool
12 :     val matchTypes : Types.ty list * Types.ty list -> bool
13 :    
14 :     val tryMatchType : Types.ty * Types.ty -> bool
15 :     val tryMatchTypes : Types.ty list * Types.ty list -> bool
16 :    
17 :     val instantiate : Types.scheme -> (Types.meta_var list * Types.ty)
18 :    
19 :     end = struct
20 :    
21 : jhr 80 structure Ty = Types
22 : jhr 81 structure MV = MetaVar
23 : jhr 96 structure TU = TypeUtil
24 : jhr 80
25 : jhr 85 (* a patch list tracks the meta variables that have been updated so that we can undo
26 :     * the effects of unification when just testing for a possible type match.
27 :     *)
28 :    
29 :     fun bindTyVar (pl, tv as Ty.TV{bind as ref NONE, ...}, ty) = (
30 :     bind := SOME ty;
31 :     pl := Ty.TYPE tv :: !pl)
32 :     | bindTyVar _ = raise Fail "rebinding type variable"
33 :    
34 :     fun bindDiffVar (pl, dv as Ty.DfV{bind as ref NONE, ...}, diff) = (
35 :     bind := SOME diff;
36 :     pl := Ty.DIFF dv :: !pl)
37 :     | bindDiffVar _ = raise Fail "rebinding differentiation variable"
38 :    
39 :     fun bindShapeVar (pl, sv as Ty.SV{bind as ref NONE, ...}, shape) = (
40 :     bind := SOME shape;
41 :     pl := Ty.SHAPE sv :: !pl)
42 :     | bindShapeVar _ = raise Fail "rebinding shape variable"
43 :    
44 :     fun bindDimVar (pl, dv as Ty.DV{bind as ref NONE, ...}, dim) = (
45 :     bind := SOME dim;
46 :     pl := Ty.DIM dv :: !pl)
47 :     | bindDimVar _ = raise Fail "rebinding dimension variable"
48 :    
49 :     fun undo pl = let
50 :     fun undo1 (Ty.TYPE(Ty.TV{bind, ...})) = bind := NONE
51 :     | undo1 (Ty.DIFF(Ty.DfV{bind, ...})) = bind := NONE
52 :     | undo1 (Ty.SHAPE(Ty.SV{bind, ...})) = bind := NONE
53 :     | undo1 (Ty.DIM(Ty.DV{bind, ...})) = bind := NONE
54 :     in
55 :     List.map undo1 (!pl)
56 :     end
57 :    
58 : jhr 81 (* FIXME: what about the bounds? *)
59 : jhr 96 fun matchDiff (pl, diff1, diff2) = (case (TU.pruneDiff diff1, TU.pruneDiff diff2)
60 : jhr 81 of (Ty.DiffConst k1, Ty.DiffConst k2) => (k1 = k2)
61 : jhr 85 | (Ty.DiffConst k, Ty.DiffVar(dv, i)) => let
62 : jhr 81 val k' = k+i
63 :     in
64 :     if k' < 0 then false
65 : jhr 85 else (bindDiffVar(pl, dv, Ty.DiffConst k'); true)
66 : jhr 81 end
67 : jhr 85 | (Ty.DiffVar(dv, i), Ty.DiffConst k) => let
68 : jhr 81 val k' = k+i
69 :     in
70 :     if k' < 0 then false
71 : jhr 85 else (bindDiffVar(pl, dv, Ty.DiffConst k'); true)
72 : jhr 81 end
73 :     | (Ty.DiffVar(dv1, i1), Ty.DiffVar(dv2, i2)) => raise Fail "unimplemented" (* FIXME *)
74 :     (* end case *))
75 :    
76 : jhr 96 fun matchDim (pl, dim1, dim2) = (case (TU.pruneDim dim1, TU.pruneDim dim2)
77 : jhr 81 of (Ty.DimConst d1, Ty.DimConst d2) => (d1 = d2)
78 : jhr 85 | (Ty.DimVar dv, dim2) => (bindDimVar(pl, dv, dim2); true)
79 :     | (dim1, Ty.DimVar dv) => (bindDimVar(pl, dv, dim1); true)
80 : jhr 81 (* end case *))
81 :    
82 : jhr 96 fun matchShape (pl, shape1, shape2) = (case (TU.pruneShape shape1, TU.pruneShape shape2)
83 : jhr 81 of (Ty.Shape dd1, Ty.Shape dd2) => let
84 :     fun chk ([], []) = true
85 : jhr 85 | chk (d1::dd1, d2::dd2) = matchDim(pl, d1, d2) andalso chk (dd1, dd2)
86 : jhr 81 | chk _ = false
87 :     in
88 :     chk (dd1, dd2)
89 :     end
90 :     | (Ty.Shape dd, Ty.ShapeExt(shape, d2)) => let
91 :     fun chk ([], _) = false
92 :     | chk ([d], revDD) =
93 : jhr 85 matchDim(pl, d, d2) andalso matchShape(pl, Ty.Shape(List.rev revDD), shape)
94 : jhr 81 | chk (d::dd, revDD) = chk(dd, d::revDD)
95 :     in
96 :     chk (dd, [])
97 :     end
98 : jhr 85 | (Ty.ShapeVar sv, shape) => (bindShapeVar (pl, sv, shape); true)
99 : jhr 81 | (Ty.ShapeExt(shape1, d1), Ty.ShapeExt(shape2, d2)) =>
100 : jhr 85 matchDim(pl, d1, d2) andalso matchShape(pl, shape1, shape2)
101 :     | (shape1, shape2) => matchShape(pl, shape2, shape1)
102 : jhr 81 (* end case *))
103 :    
104 :     (* QUESTION: do we need an occurs check? *)
105 : jhr 85 fun unifyType (pl, ty1, ty2) = let
106 : jhr 81 fun matchVar (tv1 as Ty.TV{id=id1, ...}, tv2 as Ty.TV{id=id2, ...}) =
107 :     if Stamp.same(id1, id2)
108 :     then ()
109 : jhr 85 else bindTyVar (pl, tv1, Ty.T_Var tv2)
110 : jhr 81 fun match (Ty.T_Var tv1, Ty.T_Var tv2) = (matchVar(tv1, tv2); true)
111 : jhr 85 | match (Ty.T_Var tv1, ty2) = (bindTyVar(pl, tv1, ty2); true)
112 :     | match (ty1, Ty.T_Var tv2) = (bindTyVar(pl, tv2, ty2); true)
113 : jhr 80 | match (Ty.T_Bool, Ty.T_Bool) = true
114 :     | match (Ty.T_Int, Ty.T_Int) = true
115 :     | match (Ty.T_String, Ty.T_String) = true
116 : jhr 85 | match (Ty.T_Kernel k1, Ty.T_Kernel k2) = matchDiff (pl, k1, k2)
117 :     | match (Ty.T_Tensor s1, Ty.T_Tensor s2) = matchShape (pl, s1, s2)
118 : jhr 80 | match (Ty.T_Image{dim=d1, shape=s1}, Ty.T_Image{dim=d2, shape=s2}) =
119 : jhr 85 matchDim (pl, d1, d2) andalso matchShape(pl, s1, s2)
120 : jhr 80 | match (Ty.T_Field{diff=k1, dim=d1, shape=s1}, Ty.T_Field{diff=k2, dim=d2, shape=s2}) =
121 : jhr 85 matchDiff (pl, k1, k2) andalso matchDim (pl, d1, d2) andalso matchShape(pl, s1, s2)
122 : jhr 81 | match (Ty.T_Fun(tys11, ty12), Ty.T_Fun(tys21, ty22)) =
123 : jhr 85 ListPair.allEq match (tys11, tys21) andalso match (ty12, ty22)
124 : jhr 80 | match _ = false
125 :     in
126 : jhr 96 match (TU.pruneHead ty1, TU.pruneHead ty2)
127 : jhr 80 end
128 :    
129 : jhr 85 fun matchTypes (tys1, tys2) = let
130 :     val pl = ref[]
131 :     in
132 :     ListPair.allEq (fn (ty1, ty2) => unifyType(pl, ty1, ty2)) (tys1, tys2)
133 :     end
134 : jhr 81
135 : jhr 85 fun matchType (ty1, ty2) = unifyType (ref[], ty1, ty2)
136 :    
137 :     (* try to match types; if we fail, all meta-variable bindings are undone *)
138 :     fun tryMatchType (ty1, ty2) = let
139 :     val pl = ref[]
140 :     in
141 :     unifyType(pl, ty1, ty2) orelse (undo pl; false)
142 :     end
143 :    
144 :     (* try to match types; if we fail, all meta-variable bindings are undone *)
145 :     fun tryMatchTypes (tys1, tys2) = let
146 :     val pl = ref[]
147 :     in
148 :     ListPair.allEq (fn (ty1, ty2) => unifyType(pl, ty1, ty2)) (tys1, tys2)
149 :     orelse (undo pl; false)
150 :     end
151 :    
152 : jhr 96 (* QUESTION: perhaps this function belongs in the TypeUtil module? *)
153 : jhr 81 (* instantiate a type scheme, returning the argument meta variables and the resulting type.
154 :     * Note that we assume that the scheme is closed.
155 :     *)
156 :     fun instantiate ([], ty) = ([], ty)
157 :     | instantiate (mvs, ty) = let
158 :     fun instantiateVar (mv, (mvs, env)) = let
159 :     val mv' = MV.copy mv
160 :     in
161 :     (mv'::mvs, MV.Map.insert(env, mv, mv'))
162 :     end
163 :     val (mvs, env) = List.foldl instantiateVar ([], MV.Map.empty) mvs
164 : jhr 82 fun iDiff (Ty.DiffVar(k, i)) = (case MV.Map.find(env, Ty.DIFF k)
165 :     of SOME(Ty.DIFF k) => Ty.DiffVar(k, i)
166 :     | _ => raise Fail "impossible"
167 :     (* end case *))
168 :     | iDiff diff = diff
169 :     fun iDim (Ty.DimVar dv) = (case MV.Map.find(env, Ty.DIM dv)
170 :     of SOME(Ty.DIM dv) => Ty.DimVar dv
171 :     | _ => raise Fail "impossible"
172 :     (* end case *))
173 :     | iDim dim = dim
174 :     fun iShape (Ty.ShapeVar sv) = (case MV.Map.find(env, Ty.SHAPE sv)
175 :     of SOME(Ty.SHAPE sv) => Ty.ShapeVar sv
176 :     | _ => raise Fail "impossible"
177 :     (* end case *))
178 :     | iShape (Ty.ShapeExt(shape, dim)) = Ty.ShapeExt(iShape shape, iDim dim)
179 :     | iShape (Ty.Shape dims) = Ty.Shape(List.map iDim dims)
180 : jhr 81 fun ity (Ty.T_Var tv) = (case MV.Map.find(env, Ty.TYPE tv)
181 :     of SOME(Ty.TYPE tv) => Ty.T_Var tv
182 :     | _ => raise Fail "impossible"
183 :     (* end case *))
184 : jhr 82 | ity (Ty.T_Kernel k) = Ty.T_Kernel(iDiff k)
185 :     | ity (Ty.T_Tensor shape) = Ty.T_Tensor(iShape shape)
186 :     | ity (Ty.T_Image{dim, shape}) = Ty.T_Image{dim=iDim dim, shape=iShape shape}
187 :     | ity (Ty.T_Field{diff, dim, shape}) =
188 :     Ty.T_Field{diff=iDiff diff, dim=iDim dim, shape=iShape shape}
189 :     | ity (Ty.T_Fun(dom, rng)) = Ty.T_Fun(List.map ity dom, ity rng)
190 :     | ity ty = ty
191 : jhr 81 in
192 : jhr 82 (mvs, ity ty)
193 : jhr 81 end
194 :    
195 : jhr 80 end

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