chr_integertable_store.pl

   1 /*  $Id$
   2
   3     Part of CHR (Constraint Handling Rules)
   4
   5     based on chr_hashtable_store (by Tom Schrijvers)
   6     Author:        Jon Sneyers
   7     E-mail:        Jon.Sneyers@cs.kuleuven.be
   8     WWW:           http://www.swi-prolog.org
   9     Copyright (C): 2005, K.U. Leuven
  10
  11     This program is free software; you can redistribute it and/or
  12     modify it under the terms of the GNU General Public License
  13     as published by the Free Software Foundation; either version 2
  14     of the License, or (at your option) any later version.
  15
  16     This program is distributed in the hope that it will be useful,
  17     but WITHOUT ANY WARRANTY; without even the implied warranty of
  18     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19     GNU General Public License for more details.
  20
  21     You should have received a copy of the GNU Lesser General Public
  22     License along with this library; if not, write to the Free Software
  23     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  24
  25     As a special exception, if you link this library with other files,
  26     compiled with a Free Software compiler, to produce an executable, this
  27     library does not by itself cause the resulting executable to be covered
  28     by the GNU General Public License. This exception does not however
  29     invalidate any other reasons why the executable file might be covered by
  30     the GNU General Public License.
  31 */
  32
  33 % is it safe to use nb_setarg here?
  34
  35 :- module(chr_integertable_store,
  36         [ new_iht/1,
  37           lookup_iht/3,
  38           insert_iht/3,
  39           delete_iht/3,
  40           value_iht/2
  41         ]).
  42 :- use_module(library(lists)).
  43 :- use_module(hprolog).
  44
  45 %initial_capacity(65536).
  46 %initial_capacity(1024).
  47 initial_capacity(8).
  48 %initial_capacity(2).
  49 %initial_capacity(1).
  50
  51
  52 new_iht(HT) :-
  53         initial_capacity(Capacity),
  54         new_iht(Capacity,HT).
  55
  56 new_iht(Capacity,HT) :-
  57         functor(T1,t,Capacity),
  58         HT = ht(Capacity,Table),
  59         Table = T1.
  60
  61 lookup_iht(ht(_,Table),Int,Values) :-
  62         Index is Int + 1,
  63         arg(Index,Table,Values),
  64         Values \= [].
  65 %       nonvar(Values).
  66
  67 insert_iht(HT,Int,Value) :-
  68         Index is Int + 1,
  69         arg(2,HT,Table),
  70         (arg(Index,Table,Bucket) ->
  71             ( var(Bucket) ->
  72                 Bucket = [Value]
  73             ;
  74                 setarg(Index,Table,[Value|Bucket])
  75             )
  76         ;       % index > capacity
  77                 Capacity is 1<<ceil(log(Index)/log(2)),
  78                 expand_iht(HT,Capacity),
  79                 insert_iht(HT,Int,Value)
  80         ).
  81
  82 delete_iht(ht(_,Table),Int,Value) :-
  83 %       arg(2,HT,Table),
  84         Index is Int + 1,
  85         arg(Index,Table,Bucket),
  86         ( Bucket = [_Value] ->
  87                 setarg(Index,Table,[])
  88         ;
  89                 delete_first_fail(Bucket,Value,NBucket),
  90                 setarg(Index,Table,NBucket)
  91         ).
  92 %delete_first_fail([], Y, []).
  93 %delete_first_fail([_], _, []) :- !.
  94 delete_first_fail([X | Xs], Y, Xs) :-
  95         X == Y, !.
  96 delete_first_fail([X | Xs], Y, [X | Zs]) :-
  97         delete_first_fail(Xs, Y, Zs).
  98
  99 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 100 value_iht(HT,Value) :-
 101         HT = ht(Capacity,Table),
 102         value_iht(1,Capacity,Table,Value).
 103
 104 value_iht(I,N,Table,Value) :-
 105         I =< N,
 106         arg(I,Table,Bucket),
 107         (
 108                 nonvar(Bucket),
 109                 member(Value,Bucket)
 110         ;
 111                 J is I + 1,
 112                 value_iht(J,N,Table,Value)
 113         ).
 114
 115 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 116
 117 expand_iht(HT,NewCapacity) :-
 118         HT = ht(Capacity,Table),
 119         functor(NewTable,t,NewCapacity),
 120         setarg(1,HT,NewCapacity),
 121         setarg(2,HT,NewTable),
 122         expand_copy(Table,1,Capacity,NewTable,NewCapacity).
 123
 124 expand_copy(Table,I,N,NewTable,NewCapacity) :-
 125         ( I > N ->
 126                 true
 127         ;
 128                 arg(I,Table,Bucket),
 129                 ( var(Bucket) ->
 130                         true
 131                 ;
 132                         arg(I,NewTable,Bucket)
 133                 ),
 134                 J is I + 1,
 135                 expand_copy(Table,J,N,NewTable,NewCapacity)
 136         ).