84 lines
1.8 KiB
C
84 lines
1.8 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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#include "misc.h"
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flt_add(e1,e2,e3)
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register flt_arith *e1,*e2,*e3;
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{
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/* Add two extended numbers e1 and e2, and put the result
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in e3
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*/
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flt_arith ce1, ce2;
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int diff;
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flt_status = 0;
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if ((e2->m1 | e2->m2) == 0L) {
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*e3 = *e1;
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return;
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}
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if ((e1->m1 | e1->m2) == 0L) {
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*e3 = *e2;
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return;
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}
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ce2 = *e2;
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ce1 = *e1;
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e1 = &ce1;
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e2 = &ce2;
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/* adjust mantissas to equal power */
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diff = e2->flt_exp - e1->flt_exp;
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if (diff < 0) {
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diff = -diff;
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e2->flt_exp += diff;
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flt_b64_sft(&(e2->flt_mantissa), diff);
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}
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else if (diff > 0) {
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e1->flt_exp += diff;
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flt_b64_sft(&(e1->flt_mantissa), diff);
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}
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if (e1->flt_sign != e2->flt_sign) {
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/* e2 + e1 = e2 - (-e1) */
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int tmp = ucmp(e1->m1, e2->m1);
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int tmp2 = ucmp(e1->m2, e2->m2);
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if (tmp > 0 || (tmp == 0 && tmp2 > 0)) {
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/* abs(e1) > abs(e2) */
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if (tmp2 < 0) {
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e1->m1 -= 1; /* carry in */
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}
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e1->m1 -= e2->m1;
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e1->m2 -= e2->m2;
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*e3 = *e1;
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}
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else {
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if (tmp2 > 0)
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e2->m1 -= 1; /* carry in */
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e2->m1 -= e1->m1;
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e2->m2 -= e1->m2;
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*e3 = *e2;
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}
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}
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else {
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*e3 = *e2;
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if (flt_b64_add(&e3->flt_mantissa,&e1->flt_mantissa)) {/* addition carry */
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flt_b64_sft(&e3->flt_mantissa, 1);
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e3->m1 |= 0x80000000L; /* set max bit */
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e3->flt_exp++; /* increase the exponent */
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}
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}
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flt_nrm(e3);
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flt_chk(e3);
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}
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flt_sub(e1,e2,e3)
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flt_arith *e1,*e2,*e3;
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{
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e2->flt_sign = ! e2->flt_sign;
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flt_add(e1,e2,e3);
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e2->flt_sign = ! e2->flt_sign;
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}
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