/* $Id$
Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: jan@swi.psy.uva.nl
WWW: http://www.swi-prolog.org
Copyright (C): 1985-2002, University of Amsterdam
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 Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/*#define O_DEBUG 1*/
#include "pl-incl.h"
#undef LD
#define LD LOCAL_LD
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
$btree_find_node(+Value, +Tree, -Node, -Arg)
Assuming Tree is a term x(Key, Left, Right, ...), find a (sub) node for
operating on Value. If a node with Key == Value is found Arg is unified
to 1. If such a node is not found Arg is 2 if the tree must get a new
left-node and 3 if it must get a new right-node.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
static
PRED_IMPL("$btree_find_node", 4, btree_find_node, 0)
{ PRED_LD
Word t, k;
Functor f;
functor_t fd;
int arity;
k = valTermRef(A1);
t = valTermRef(A2);
deRef(k);
deRef(t);
if ( !isTerm(*t) )
return PL_error(NULL, 0, NULL, ERR_TYPE, ATOM_btree, A2);
f = valueTerm(*t);
fd = f->definition;
arity = arityFunctor(fd);
if ( arity < 3 )
return PL_error(NULL, 0, NULL, ERR_TYPE, ATOM_btree, A2);
for(;;)
{ Word a = &f->arguments[0];
Word n;
int d = compareStandard(k, a, FALSE PASS_LD);
int arg;
if ( d == CMP_ERROR )
return FALSE;
if ( d == CMP_EQUAL )
{ if ( unify_ptrs(t, valTermRef(A3), ALLOW_GC|ALLOW_SHIFT PASS_LD) &&
PL_unify_integer(A4, 1) )
succeed;
fail;
}
arg = (d == CMP_LESS ? 1 : 2);
n = a+arg;
deRef(n);
DEBUG(1, Sdprintf("Taking %s\n", arg == 1 ? "left" : "right"));
if ( !isTerm(*n) )
{ nomatch:
if ( unify_ptrs(t, valTermRef(A3), ALLOW_GC|ALLOW_SHIFT PASS_LD) &&
PL_unify_integer(A4, arg+1) )
succeed;
fail;
}
f = valueTerm(*n);
if ( f->definition != fd )
goto nomatch;
t = n;
}
succeed;
}
/*******************************
* PUBLISH PREDICATES *
*******************************/
BeginPredDefs(btree)
PRED_DEF("$btree_find_node", 4, btree_find_node, 0)
EndPredDefs