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(*
Copyright (c) 2000
Cambridge University Technical Services Limited
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*)
structure UniversalTable :
sig
type universal;
type 'a tag;
type univTable;
val makeUnivTable: unit -> univTable;
val univEnter: univTable * 'a tag * string * 'a -> unit;
val univLookup: univTable * 'a tag * string -> 'a option;
val univDelete: univTable * 'a tag * string -> unit;
val fold: (string * universal * 'a -> 'a) -> 'a -> univTable -> 'a
val app: (string * universal -> unit) -> univTable -> unit
val univFold: univTable * (string * universal * 'a -> 'a) * 'a -> 'a
(* Freeze a mutable table so it is immutable. *)
val univFreeze: univTable -> univTable
end =
struct
open Misc;
open HashTable;
open Universal;
type universal = universal
datatype univTable = Table of universal list hash
fun makeUnivTable() = Table (hashMake 10); (* Choose a number. *)
fun univLookup (Table tab, t:'a tag, name:string) : 'a option =
let
fun search [] = NONE
| search (H::T) = if tagIs t H then SOME (tagProject t H) else search T;
in
case hashSub (tab, name) of
NONE => NONE
| SOME t => search t
end
fun univEnter (Table tab, t:'a tag, name:string, v:'a) : unit =
let
val u = tagInject t v;
(* If there is already an entry we add it to the list,
otherwise we start a new list. *)
fun search [] = [u]
| search (H::T) = if tagIs t H then u :: T else H :: search T;
val newList =
case hashSub (tab, name) of
SOME v => search v
| NONE => [u]
in
hashSet (tab, name, newList)
end;
fun univDelete (Table tab, t:'a tag, name:string) : unit =
let
fun search [] = []
| search (H::T) = if tagIs t H then T else H :: search T;
in
case hashSub (tab, name) of
SOME l => hashSet (tab, name, search l)
| NONE => ()
end;
fun fold f acc (Table table) =
let
fun foldHashEntry (s, l, acc) =
List.foldl (fn (c, a) => f (s, c, a)) acc l
in
HashTable.fold foldHashEntry acc table
end
fun app f = fold (fn (s, c, ()) => f (s, c)) ()
(* Backwards compatibility. *)
fun univFold (t, f, acc) = fold f acc t
fun univFreeze (Table h) = Table(hashFreeze h)
end (* UniversalTable *);
|
