author | wenzelm |
Mon, 01 Jun 2009 15:26:00 +0200 | |
changeset 31326 | deddd77112b7 |
parent 29269 | 5c25a2012975 |
child 31977 | e03059ae2d82 |
permissions | -rw-r--r-- |
20513 | 1 |
(* Title: Pure/term_subst.ML |
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Author: Makarius |
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Efficient term substitution -- avoids copying. |
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*) |
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signature TERM_SUBST = |
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sig |
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val generalize: string list * string list -> int -> term -> term |
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val generalizeT: string list -> int -> typ -> typ |
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val generalize_option: string list * string list -> int -> term -> term option |
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val generalizeT_option: string list -> int -> typ -> typ option |
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val instantiateT_maxidx: ((indexname * sort) * (typ * int)) list -> typ -> int -> typ * int |
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val instantiate_maxidx: |
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((indexname * sort) * (typ * int)) list * ((indexname * typ) * (term * int)) list -> |
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term -> int -> term * int |
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val instantiate: ((indexname * sort) * typ) list * ((indexname * typ) * term) list -> |
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term -> term |
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val instantiateT: ((indexname * sort) * typ) list -> typ -> typ |
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val instantiate_option: ((indexname * sort) * typ) list * ((indexname * typ) * term) list -> |
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term -> term option |
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val instantiateT_option: ((indexname * sort) * typ) list -> typ -> typ option |
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val zero_var_indexes: term -> term |
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val zero_var_indexes_inst: term list -> |
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((indexname * sort) * typ) list * ((indexname * typ) * term) list |
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end; |
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structure TermSubst: TERM_SUBST = |
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struct |
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(* generalization of fixed variables *) |
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local |
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exception SAME; |
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fun generalizeT_same [] _ _ = raise SAME |
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| generalizeT_same tfrees idx ty = |
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let |
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fun gen_typ (Type (a, Ts)) = Type (a, gen_typs Ts) |
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| gen_typ (TFree (a, S)) = |
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if member (op =) tfrees a then TVar ((a, idx), S) |
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else raise SAME |
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| gen_typ _ = raise SAME |
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and gen_typs (T :: Ts) = |
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(gen_typ T :: (gen_typs Ts handle SAME => Ts) |
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handle SAME => T :: gen_typs Ts) |
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| gen_typs [] = raise SAME; |
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in gen_typ ty end; |
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fun generalize_same ([], []) _ _ = raise SAME |
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| generalize_same (tfrees, frees) idx tm = |
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let |
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val genT = generalizeT_same tfrees idx; |
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fun gen (Free (x, T)) = |
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if member (op =) frees x then |
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Var (Name.clean_index (x, idx), genT T handle SAME => T) |
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else Free (x, genT T) |
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| gen (Var (xi, T)) = Var (xi, genT T) |
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| gen (Const (c, T)) = Const (c, genT T) |
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| gen (Bound _) = raise SAME |
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| gen (Abs (x, T, t)) = |
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(Abs (x, genT T, gen t handle SAME => t) |
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handle SAME => Abs (x, T, gen t)) |
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| gen (t $ u) = (gen t $ (gen u handle SAME => u) handle SAME => t $ gen u); |
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in gen tm end; |
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in |
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fun generalize names i tm = generalize_same names i tm handle SAME => tm; |
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fun generalizeT names i ty = generalizeT_same names i ty handle SAME => ty; |
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fun generalize_option names i tm = SOME (generalize_same names i tm) handle SAME => NONE; |
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fun generalizeT_option names i ty = SOME (generalizeT_same names i ty) handle SAME => NONE; |
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end; |
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(* instantiation of schematic variables (types before terms) -- recomputes maxidx *) |
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local |
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fun no_index (x, y) = (x, (y, ~1)); |
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fun no_indexes1 inst = map no_index inst; |
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fun no_indexes2 (inst1, inst2) = (map no_index inst1, map no_index inst2); |
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exception SAME; |
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fun instantiateT_same maxidx instT ty = |
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let |
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fun maxify i = if i > ! maxidx then maxidx := i else (); |
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fun subst_typ (Type (a, Ts)) = Type (a, subst_typs Ts) |
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| subst_typ (TVar ((a, i), S)) = |
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(case AList.lookup Term.eq_tvar instT ((a, i), S) of |
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SOME (T, j) => (maxify j; T) |
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| NONE => (maxify i; raise SAME)) |
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| subst_typ _ = raise SAME |
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and subst_typs (T :: Ts) = |
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(subst_typ T :: (subst_typs Ts handle SAME => Ts) |
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handle SAME => T :: subst_typs Ts) |
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| subst_typs [] = raise SAME; |
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in subst_typ ty end; |
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fun instantiate_same maxidx (instT, inst) tm = |
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let |
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fun maxify i = if i > ! maxidx then maxidx := i else (); |
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val substT = instantiateT_same maxidx instT; |
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fun subst (Const (c, T)) = Const (c, substT T) |
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| subst (Free (x, T)) = Free (x, substT T) |
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| subst (Var ((x, i), T)) = |
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let val (T', same) = (substT T, false) handle SAME => (T, true) in |
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(case AList.lookup Term.eq_var inst ((x, i), T') of |
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SOME (t, j) => (maxify j; t) |
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| NONE => (maxify i; if same then raise SAME else Var ((x, i), T'))) |
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end |
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| subst (Bound _) = raise SAME |
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| subst (Abs (x, T, t)) = |
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(Abs (x, substT T, subst t handle SAME => t) |
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handle SAME => Abs (x, T, subst t)) |
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| subst (t $ u) = (subst t $ (subst u handle SAME => u) handle SAME => t $ subst u); |
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in subst tm end; |
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in |
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fun instantiateT_maxidx instT ty i = |
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let val maxidx = ref i |
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in (instantiateT_same maxidx instT ty handle SAME => ty, ! maxidx) end; |
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fun instantiate_maxidx insts tm i = |
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let val maxidx = ref i |
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in (instantiate_same maxidx insts tm handle SAME => tm, ! maxidx) end; |
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fun instantiateT [] ty = ty |
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| instantiateT instT ty = |
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(instantiateT_same (ref ~1) (no_indexes1 instT) ty handle SAME => ty); |
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fun instantiate ([], []) tm = tm |
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| instantiate insts tm = |
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(instantiate_same (ref ~1) (no_indexes2 insts) tm handle SAME => tm); |
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fun instantiateT_option [] _ = NONE |
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| instantiateT_option instT ty = |
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(SOME (instantiateT_same (ref ~1) (no_indexes1 instT) ty) handle SAME => NONE); |
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fun instantiate_option ([], []) _ = NONE |
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| instantiate_option insts tm = |
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(SOME (instantiate_same (ref ~1) (no_indexes2 insts) tm) handle SAME => NONE); |
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end; |
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(* zero var indexes *) |
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fun zero_var_inst vars = |
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fold (fn v as ((x, i), X) => fn (inst, used) => |
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let |
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val ([x'], used') = Name.variants [if Name.is_bound x then "u" else x] used; |
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in if x = x' andalso i = 0 then (inst, used') else ((v, ((x', 0), X)) :: inst, used') end) |
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vars ([], Name.context) |> #1; |
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fun zero_var_indexes_inst ts = |
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let |
29269
5c25a2012975
moved term order operations to structure TermOrd (cf. Pure/term_ord.ML);
wenzelm
parents:
21607
diff
changeset
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val tvars = sort TermOrd.tvar_ord (fold Term.add_tvars ts []); |
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val instT = map (apsnd TVar) (zero_var_inst tvars); |
29269
5c25a2012975
moved term order operations to structure TermOrd (cf. Pure/term_ord.ML);
wenzelm
parents:
21607
diff
changeset
|
167 |
val vars = sort TermOrd.var_ord (map (apsnd (instantiateT instT)) (fold Term.add_vars ts [])); |
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val inst = map (apsnd Var) (zero_var_inst vars); |
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in (instT, inst) end; |
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fun zero_var_indexes t = instantiate (zero_var_indexes_inst [t]) t; |
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end; |