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(* Title: Pure/data.ML
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ID: $Id$
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Author: Markus Wenzel, TU Muenchen
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Arbitrarily typed data. Fools the ML type system via exception
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constructors.
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*)
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type object = exn;
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signature DATA =
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sig
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type T
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val empty: T
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val merge: T * T -> T
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val prep_ext: T -> T
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val kinds: T -> string list
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val init: T -> string -> object ->
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(object -> object) -> (object * object -> object) -> (object -> unit) -> T
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val get: T -> string -> object
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val put: T -> string -> object -> T
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val print: T -> string -> unit
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end;
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structure Data: DATA =
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struct
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(* datatype T *)
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datatype T = Data of
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(object * (*value*)
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((object -> object) * (*prepare extend method*)
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(object * object -> object) * (*merge and prepare extend method*)
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(object -> unit))) (*print method*)
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Symtab.table;
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val empty = Data Symtab.null;
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fun kinds (Data tab) = map fst (Symtab.dest tab);
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(* errors *)
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fun err_method name kind =
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error ("Error while invoking " ^ quote kind ^ " " ^ name ^ " method");
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fun err_dup_init kind =
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error ("Duplicate initialization of " ^ quote kind ^ " data");
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fun err_uninit kind =
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error ("Tried to access uninitialized " ^ quote kind ^ " data");
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(* prepare data *)
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fun merge (Data tab1, Data tab2) =
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let
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val data1 = Symtab.dest tab1;
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val data2 = Symtab.dest tab2;
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val all_data = data1 @ data2;
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val kinds = distinct (map fst all_data);
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fun entry data kind =
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(case assoc (data, kind) of
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None => []
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| Some x => [(kind, x)]);
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fun merge_entries [(kind, (e, mths as (ext, _, _)))] =
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(kind, (ext e handle _ => err_method "prep_ext" kind, mths))
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| merge_entries [(kind, (e1, mths as (_, mrg, _))), (_, (e2, _))] =
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(kind, (mrg (e1, e2) handle _ => err_method "merge" kind, mths))
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| merge_entries _ = sys_error "merge_entries";
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val data = map (fn k => merge_entries (entry data1 k @ entry data2 k)) kinds;
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in Data (Symtab.make data) end;
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fun prep_ext data = merge (data, empty);
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fun init (Data tab) kind e ext mrg prt =
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Data (Symtab.update_new ((kind, (e, (ext, mrg, prt))), tab))
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handle Symtab.DUPLICATE _ => err_dup_init kind;
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(* access data *)
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fun lookup tab kind =
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(case Symtab.lookup (tab, kind) of
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Some x => x
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| None => err_uninit kind);
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fun get (Data tab) kind = fst (lookup tab kind);
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fun put (Data tab) kind e =
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Data (Symtab.update ((kind, (e, snd (lookup tab kind))), tab));
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fun print (Data tab) kind =
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let val (e, (_, _, prt)) = lookup tab kind
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in prt e handle _ => err_method "print" kind end;
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end;
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