author | wenzelm |
Mon, 06 Oct 1997 18:21:00 +0200 | |
changeset 3775 | a99fdf465dfb |
parent 2229 | 64acb485ecce |
child 5689 | ffecea547501 |
permissions | -rw-r--r-- |
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(* Title: Pure/Syntax/ast.ML |
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ID: $Id$ |
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Author: Markus Wenzel, TU Muenchen |
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Abstract syntax trees, translation rules, matching and normalization of asts. |
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*) |
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signature AST0 = |
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sig |
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datatype ast = |
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Constant of string | |
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Variable of string | |
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Appl of ast list |
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exception AST of string * ast list |
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end; |
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signature AST1 = |
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sig |
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include AST0 |
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val mk_appl: ast -> ast list -> ast |
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val str_of_ast: ast -> string |
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val pretty_ast: ast -> Pretty.T |
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val pretty_rule: ast * ast -> Pretty.T |
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val pprint_ast: ast -> pprint_args -> unit |
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val trace_norm_ast: bool ref |
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val stat_norm_ast: bool ref |
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end; |
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signature AST = |
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sig |
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include AST1 |
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val head_of_rule: ast * ast -> string |
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val rule_error: ast * ast -> string option |
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val fold_ast: string -> ast list -> ast |
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val fold_ast_p: string -> ast list * ast -> ast |
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val unfold_ast: string -> ast -> ast list |
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val unfold_ast_p: string -> ast -> ast list * ast |
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val normalize: bool -> bool -> (string -> (ast * ast) list) option -> ast -> ast |
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val normalize_ast: (string -> (ast * ast) list) option -> ast -> ast |
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end; |
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structure Ast : AST = |
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struct |
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(** abstract syntax trees **) |
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(*asts come in two flavours: |
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- ordinary asts representing terms and typs: Variables are (often) treated |
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like Constants; |
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- patterns used as lhs and rhs in rules: Variables are placeholders for |
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proper asts*) |
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datatype ast = |
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Constant of string | (*"not", "_abs", "fun"*) |
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Variable of string | (*x, ?x, 'a, ?'a*) |
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Appl of ast list; (*(f x y z), ("fun" 'a 'b), ("_abs" x t)*) |
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(*the list of subasts of an Appl node has to contain at least 2 elements, i.e. |
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there are no empty asts or nullary applications; use mk_appl for convenience*) |
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fun mk_appl f [] = f |
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| mk_appl f args = Appl (f :: args); |
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(*exception for system errors involving asts*) |
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exception AST of string * ast list; |
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(** print asts in a LISP-like style **) |
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(* str_of_ast *) |
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fun str_of_ast (Constant a) = quote a |
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| str_of_ast (Variable x) = x |
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| str_of_ast (Appl asts) = "(" ^ (space_implode " " (map str_of_ast asts)) ^ ")"; |
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(* pretty_ast *) |
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fun pretty_ast (Constant a) = Pretty.str (quote a) |
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| pretty_ast (Variable x) = Pretty.str x |
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| pretty_ast (Appl asts) = |
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Pretty.enclose "(" ")" (Pretty.breaks (map pretty_ast asts)); |
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(* pprint_ast *) |
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val pprint_ast = Pretty.pprint o pretty_ast; |
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(* pretty_rule *) |
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fun pretty_rule (lhs, rhs) = |
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Pretty.block [pretty_ast lhs, Pretty.str " ->", Pretty.brk 2, pretty_ast rhs]; |
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(* head_of_ast, head_of_rule *) |
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fun head_of_ast (Constant a) = Some a |
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| head_of_ast (Appl (Constant a :: _)) = Some a |
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| head_of_ast _ = None; |
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fun head_of_rule (lhs, _) = the (head_of_ast lhs); |
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(** check translation rules **) |
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(*a wellformed rule (lhs, rhs): (ast * ast) obeys the following conditions: |
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- the head of lhs is a constant, |
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- the lhs has unique vars, |
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- vars of rhs is subset of vars of lhs*) |
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fun rule_error (rule as (lhs, rhs)) = |
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let |
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fun vars_of (Constant _) = [] |
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| vars_of (Variable x) = [x] |
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| vars_of (Appl asts) = flat (map vars_of asts); |
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fun unique (x :: xs) = not (x mem xs) andalso unique xs |
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| unique [] = true; |
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val lvars = vars_of lhs; |
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val rvars = vars_of rhs; |
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in |
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if is_none (head_of_ast lhs) then Some "lhs has no constant head" |
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else if not (unique lvars) then Some "duplicate vars in lhs" |
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else if not (rvars subset lvars) then Some "rhs contains extra variables" |
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else None |
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end; |
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(** ast translation utilities **) |
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(* fold asts *) |
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fun fold_ast _ [] = raise Match |
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| fold_ast _ [y] = y |
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| fold_ast c (x :: xs) = Appl [Constant c, x, fold_ast c xs]; |
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fun fold_ast_p c = foldr (fn (x, xs) => Appl [Constant c, x, xs]); |
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(* unfold asts *) |
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fun unfold_ast c (y as Appl [Constant c', x, xs]) = |
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if c = c' then x :: (unfold_ast c xs) else [y] |
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| unfold_ast _ y = [y]; |
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fun unfold_ast_p c (y as Appl [Constant c', x, xs]) = |
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if c = c' then apfst (cons x) (unfold_ast_p c xs) |
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else ([], y) |
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| unfold_ast_p _ y = ([], y); |
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(** normalization of asts **) |
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(* tracing options *) |
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val trace_norm_ast = ref false; |
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val stat_norm_ast = ref false; |
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(* simple env *) |
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structure Env = |
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struct |
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val empty = []; |
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val add = op ::; |
|
2229
64acb485ecce
Eta-expansion of a function definition, for value polymorphism
paulson
parents:
1506
diff
changeset
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fun get (alist,x) = the (assoc (alist,x)); |
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end; |
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(* match *) |
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fun match ast pat = |
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let |
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exception NO_MATCH; |
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1127
42ec82147d83
changed macro expander such that patterns also match prefixes of appls;
wenzelm
parents:
922
diff
changeset
|
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fun mtch (Constant a) (Constant b) env = |
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if a = b then env else raise NO_MATCH |
1127
42ec82147d83
changed macro expander such that patterns also match prefixes of appls;
wenzelm
parents:
922
diff
changeset
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| mtch (Variable a) (Constant b) env = |
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if a = b then env else raise NO_MATCH |
1127
42ec82147d83
changed macro expander such that patterns also match prefixes of appls;
wenzelm
parents:
922
diff
changeset
|
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| mtch ast (Variable x) env = Env.add ((x, ast), env) |
42ec82147d83
changed macro expander such that patterns also match prefixes of appls;
wenzelm
parents:
922
diff
changeset
|
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| mtch (Appl asts) (Appl pats) env = mtch_lst asts pats env |
42ec82147d83
changed macro expander such that patterns also match prefixes of appls;
wenzelm
parents:
922
diff
changeset
|
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| mtch _ _ _ = raise NO_MATCH |
42ec82147d83
changed macro expander such that patterns also match prefixes of appls;
wenzelm
parents:
922
diff
changeset
|
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and mtch_lst (ast :: asts) (pat :: pats) env = |
42ec82147d83
changed macro expander such that patterns also match prefixes of appls;
wenzelm
parents:
922
diff
changeset
|
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mtch_lst asts pats (mtch ast pat env) |
42ec82147d83
changed macro expander such that patterns also match prefixes of appls;
wenzelm
parents:
922
diff
changeset
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| mtch_lst [] [] env = env |
42ec82147d83
changed macro expander such that patterns also match prefixes of appls;
wenzelm
parents:
922
diff
changeset
|
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| mtch_lst _ _ _ = raise NO_MATCH; |
42ec82147d83
changed macro expander such that patterns also match prefixes of appls;
wenzelm
parents:
922
diff
changeset
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195 |
|
42ec82147d83
changed macro expander such that patterns also match prefixes of appls;
wenzelm
parents:
922
diff
changeset
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val (head, args) = |
42ec82147d83
changed macro expander such that patterns also match prefixes of appls;
wenzelm
parents:
922
diff
changeset
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(case (ast, pat) of |
42ec82147d83
changed macro expander such that patterns also match prefixes of appls;
wenzelm
parents:
922
diff
changeset
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(Appl asts, Appl pats) => |
42ec82147d83
changed macro expander such that patterns also match prefixes of appls;
wenzelm
parents:
922
diff
changeset
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let val a = length asts and p = length pats in |
42ec82147d83
changed macro expander such that patterns also match prefixes of appls;
wenzelm
parents:
922
diff
changeset
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if a > p then (Appl (take (p, asts)), drop (p, asts)) |
42ec82147d83
changed macro expander such that patterns also match prefixes of appls;
wenzelm
parents:
922
diff
changeset
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else (ast, []) |
42ec82147d83
changed macro expander such that patterns also match prefixes of appls;
wenzelm
parents:
922
diff
changeset
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end |
42ec82147d83
changed macro expander such that patterns also match prefixes of appls;
wenzelm
parents:
922
diff
changeset
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| _ => (ast, [])); |
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in |
1127
42ec82147d83
changed macro expander such that patterns also match prefixes of appls;
wenzelm
parents:
922
diff
changeset
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Some (mtch head pat Env.empty, args) handle NO_MATCH => None |
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end; |
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(* normalize *) |
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(*the normalizer works yoyo-like: top-down, bottom-up, top-down, ...*) |
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fun normalize trace stat get_rules pre_ast = |
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let |
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val passes = ref 0; |
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val lookups = ref 0; |
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val failed_matches = ref 0; |
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val changes = ref 0; |
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fun subst _ (ast as Constant _) = ast |
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| subst env (Variable x) = Env.get (env, x) |
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| subst env (Appl asts) = Appl (map (subst env) asts); |
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fun try_rules ast ((lhs, rhs) :: pats) = |
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(case match ast lhs of |
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1127
42ec82147d83
changed macro expander such that patterns also match prefixes of appls;
wenzelm
parents:
922
diff
changeset
|
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Some (env, args) => |
42ec82147d83
changed macro expander such that patterns also match prefixes of appls;
wenzelm
parents:
922
diff
changeset
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(inc changes; Some (mk_appl (subst env rhs) args)) |
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| None => (inc failed_matches; try_rules ast pats)) |
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| try_rules _ [] = None; |
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fun try ast a = (inc lookups; try_rules ast (the get_rules a)); |
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fun rewrite (ast as Constant a) = try ast a |
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| rewrite (ast as Variable a) = try ast a |
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| rewrite (ast as Appl (Constant a :: _)) = try ast a |
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| rewrite (ast as Appl (Variable a :: _)) = try ast a |
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| rewrite _ = None; |
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fun rewrote old_ast new_ast = |
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if trace then |
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writeln ("rewrote: " ^ str_of_ast old_ast ^ " -> " ^ str_of_ast new_ast) |
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else (); |
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fun norm_root ast = |
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(case rewrite ast of |
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Some new_ast => (rewrote ast new_ast; norm_root new_ast) |
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| None => ast); |
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fun norm ast = |
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(case norm_root ast of |
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Appl sub_asts => |
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let |
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val old_changes = ! changes; |
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val new_ast = Appl (map norm sub_asts); |
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in |
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if old_changes = ! changes then new_ast else norm_root new_ast |
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end |
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| atomic_ast => atomic_ast); |
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fun normal ast = |
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let |
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val old_changes = ! changes; |
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val new_ast = norm ast; |
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in |
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inc passes; |
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if old_changes = ! changes then new_ast else normal new_ast |
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end; |
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val _ = if trace then writeln ("pre: " ^ str_of_ast pre_ast) else (); |
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val post_ast = if is_some get_rules then normal pre_ast else pre_ast; |
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in |
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if trace orelse stat then |
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writeln ("post: " ^ str_of_ast post_ast ^ "\nnormalize: " ^ |
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string_of_int (! passes) ^ " passes, " ^ |
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string_of_int (! lookups) ^ " lookups, " ^ |
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string_of_int (! changes) ^ " changes, " ^ |
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string_of_int (! failed_matches) ^ " matches failed") |
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else (); |
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post_ast |
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end; |
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(* normalize_ast *) |
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fun normalize_ast get_rules ast = |
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normalize (! trace_norm_ast) (! stat_norm_ast) get_rules ast; |
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end; |
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