IPRESBEZ.c,v

head	1.2;
access;
symbols;
locks
	saclib:1.2; strict;
comment	@ * @;


1.2
date	99.03.28.19.04.34;	author George;	state bug;
branches;
next	1.1;

1.1
date	99.03.21.19.18.26;	author George;	state new;
branches;
next	;


desc
@Integral polynomial resultant, Bezout.
@


1.2
log
@Corrected Step2.
@
text
@/*======================================================================
                      C <- IPRESBEZ(r,A,B)

Integral polynomial resultant, Bezout.

Inputs
   r    : a positive beta digit.
   A, B : integral polynomials of positive degrees.

Output
   C : the reultant of A and B with respect to the main variable.

Method
   The Bezout matrix of A and B is computed and its determinant
is computed by minors evaluation.
======================================================================*/
#include "saclib.h"

Word IPRESBEZ(r,A,B)
	BDigit r;
        Word A,B;
{
	BDigit s;
        Word Ap,Bp,M,R;

Step1: /* Interchange A and B if necessary. */
	if (PDEG(A) >= PDEG(B)) {
	   Ap = A;
	   Bp = B;
	   s = 1; }
	else {
	   Ap = B;
	   Bp = A;
	   s = -1; }

Step2: /* Comstruct the Bezout matrix. */
	M = IPBEZM(r,Ap,Bp);

Step3: /* Compute the determinant. */
	R = MAIPDME(r-1,M);

Step4: /* Adjust sign if necessary. */
	if (s < 0)
	   R = IPNEG(r-1,R);

Return: /* Return R. */
	return(R);
}
@


1.1
log
@Initial revision
@
text
@d23 1
a23 1
	BDigit m,s;
d37 1
a37 1
	M = IPBEZM(r,A,B);
d40 1
a40 2
	m = PDEG(Ap);
	R = MAIPDME(r-1,m,M);
d45 3
@