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// file kernel/n/c/cmp.c: comparison of natural integers
/*-----------------------------------------------------------------------+
| Copyright 2005-2006, Michel Quercia (michel.quercia@prepas.org) |
| |
| This file is part of Numerix. Numerix 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. |
| |
| The Numerix 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 the GNU MP Library; see the file COPYING. If not, |
| write to the Free Software Foundation, Inc., 59 Temple Place - |
| Suite 330, Boston, MA 02111-1307, USA. |
+-----------------------------------------------------------------------+
| |
| Comparaison |
| |
+-----------------------------------------------------------------------*/
/*
entre :
a = naturel de longueur la
b = naturel de longueur lb
sortie :
1 si a > b, 0 si a = b, -1 si a < b
*/
#ifndef assembly_sn_cmp
long xn(cmp)(chiffre *a, long la, chiffre *b, long lb) {
/* limine les zros de tte */
while ((la > 0) && (a[la-1] == 0)) la--;
while ((lb > 0) && (b[lb-1] == 0)) lb--;
/* compare les longeurs */
if (la < lb) return(-1);
if (la > lb) return( 1);
/* compare les chiffres */
while ((la > 0) && (a[la-1] == b[la-1])) la--;
if (la == 0) return(0);
if (a[la-1] < b[la-1]) return(-1);
return(1);
}
#endif /* assembly_sn_cmp */
/*
entre :
a = naturel de longueur la
b = naturel de longueur lb
contraintes :
lb >= la, lb > 0, le chiffre de poids fort de b est non nul
sortie :
1 si 2a > b, 0 si 2a = b, -1 si 2a < b
*/
#ifndef assembly_sn_cmp2
long xn(cmp2)(chiffre *a, long la, chiffre *b, long lb) {
#ifdef zdouble
zdouble r;
/* a trop court => 2a < b */
if (la < lb-1) return(-1);
/*
mmes longueurs 1 prs : calcule 2a-b par chiffres dcroissants
et arrte ds que le signe de la diffrence est connu
*/
if (la == lb) r = 2*((ndouble)a[lb-1]) - (ndouble)b[lb-1];
else r = - (ndouble)b[lb-1];
for (lb--; (lb) && (r <= 0) && (r >= -1); lb--) {
r = (r << HW) + 2*((ndouble)a[lb-1]) - (ndouble)b[lb-1];
}
return((r > 0) ? 1 : (r) ? -1 : 0);
#else
chiffre r,s,t;
/* a trop court => 2a < b */
if (la < lb-1) return(-1);
/*
mmes longueurs 1 prs : calcule 2a-b par chiffres dcroissants
et arrte ds que le signe de la diffrence est connu
*/
s = (la == lb) ? a[lb-1] : 0;
t = 2*s; r = (t < s);
s = t - b[lb-1]; r -= (s > t);
for (lb--; (lb) && (r == s) && ((r == 0) || (r == (BASE_2)+(BASE_2-1))); lb--) {
s = a[lb-1];
t = 2*s; r += (t < s);
s = t - b[lb-1]; r -= (s > t);
}
return((r == 1) ? 1 : (r) ? -1 : (s != 0));
#endif /* zdouble */
}
#endif /* assembly_sn_cmp2 */
|
