51 lines
1.1 KiB
C
51 lines
1.1 KiB
C
/*
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(c) copyright 1988 by the Vrije Universiteit, Amsterdam, The Netherlands.
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See the copyright notice in the ACK home directory, in the file "Copyright".
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*/
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/* $Header$ */
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/*
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SUBTRACT 2 EXTENDED FORMAT NUMBERS
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*/
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#include "FP_types.h"
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sub_ext(e1,e2)
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EXTEND *e1,*e2;
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{
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if ((e2->m1 | e2->m2) == 0L) {
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return;
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}
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if ((e1->m1 | e1->m2) == 0L) {
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*e1 = *e2;
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e1->sign = e2->sign ? 0 : 1;
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return;
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}
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sft_ext(e1, e2);
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if (e1->sign != e2->sign) {
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/* e1 - e2 = e1 + (-e2) */
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if (b64_add(&e1->m1,&e2->m1)) { /* addition carry */
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b64_rsft(&e1->m1); /* shift mantissa one bit RIGHT */
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e1->m1 |= 0x80000000L; /* set max bit */
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e1->exp++; /* increase the exponent */
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}
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}
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else if (e2->m1 > e1->m1 ||
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(e2->m1 == e1->m1 && e2->m2 > e1->m2)) {
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/* abs(e2) > abs(e1) */
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if (e1->m2 > e2->m2) {
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e2->m1 -= 1; /* carry in */
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}
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e2->m1 -= e1->m1;
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e2->m2 -= e1->m2;
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*e1 = *e2;
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e1->sign = e2->sign ? 0 : 1;
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}
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else {
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if (e2->m2 > e1->m2)
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e1->m1 -= 1; /* carry in */
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e1->m1 -= e2->m1;
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e1->m2 -= e2->m2;
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}
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nrm_ext(e1);
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}
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