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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;
type 'a iter;
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 univOver: univTable -> (string * universal) iter;
val univFold: univTable * (string * universal * 'a -> 'a) * 'a -> 'a;
val univOverSpecific: univTable * 'a tag -> (string * 'a) iter;
(* Freeze a mutable table so it is immutable. *)
val univFreeze: univTable -> univTable
end =
struct
local
open Misc;
open HashTable;
open Universal;
in
type universal = universal
type 'a tag = 'a tag;
type 'a iter = 'a iter;
abstype univTable = Table of universal list hash
with
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;
local
fun fst (a,b) = a;
fun snd (a,b) = b;
in
fun univOver (Table tab) = (* Iterator over all the entries. *)
let
fun continue (_,[]) = false
| continue _ = true;
fun value (_,[]) =
raise InternalError "UniversalTable.univOver.value"
| value (i,H::_) = (fst (Value i),H);
(* Get the next table entry which has something in it. *)
fun nextList i =
let
val nt = Next i;
in
if Continue nt (* Have we reached the end ? *)
then
(* No, but the entry may be empty if it has been deleted. *)
case snd (Value nt) of
[] => nextList nt
| nl => (nt,nl)
else
(nt,[]) (* At the end *)
end;
(* Return the next FULL entry. *)
fun next (ti,[]) =
raise InternalError "UniversalTable.univOver.next"
| next (ti,[x]) = makeIter (nextList ti)
(* Finished one list - get the next. *)
| next (ti,_::T) = makeIter (ti,T)
and makeIter i =
Iter
{ continue = continue i,
next = fn () => next i,
value = fn () => value i
};
val t1 = hashOver tab;
in
makeIter
(if Continue t1
then
case snd (Value t1) of
[] => nextList t1
| l1 => (t1,l1)
else
(t1,[]))
end;
(* Iterator over entries with a specific tag. *)
fun univOverSpecific (tab : univTable, t:'a tag) =
let
fun tagMatches i = tagIs t (snd (Value i));
(* Return the next entry with the specific tag *)
fun continue (n : (string * universal) iter) : bool =
Continue n andalso
(tagMatches n orelse continue (Next n));
fun try (n : (string * universal) iter) : (string * 'a) iter =
if Continue n
then if tagMatches n
then makeIter n
else try (Next n)
else makeIter n (* ??? SPF/18/8/94 *)
and makeIter (i : (string * universal) iter) : (string * 'a) iter =
Iter
{
continue = continue i, (* was "Continue i" (SPF 18/8/94) *)
next = fn () => try (Next i),
value = fn () =>
let
val (s,u) = Value i
in
(s, tagProject t u)
end
};
in
try (univOver tab)
end;
fun univFold (table, f, acc) =
let
fun foldF i acc =
if not (Continue i)
then acc
else let
val (name,u) = Value i;
in
foldF (Next i) (f (name, u, acc))
end;
in
foldF (univOver table) acc
end;
end (* local *);
fun univFreeze (Table h) = Table(hashFreeze h)
end (* with *);
end (* local *);
end (* UniversalTable *);
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