55 lines
969 B
C
55 lines
969 B
C
/*
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* (c) copyright 1987 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 <math.h>
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#include <float.h>
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#include <errno.h>
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double
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ldexp(double fl, int exp)
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{
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int sign = 1;
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int currexp;
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if (isnan(fl)) {
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errno = EDOM;
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return fl;
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}
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if (fl == 0.0) return 0.0;
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if (fl<0) {
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fl = -fl;
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sign = -1;
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}
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if (fl > DBL_MAX) { /* for infinity */
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errno = ERANGE;
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return sign * fl;
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}
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fl = frexp(fl,&currexp);
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exp += currexp;
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if (exp > 0) {
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if (exp > DBL_MAX_EXP) {
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errno = ERANGE;
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return sign * HUGE_VAL;
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}
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while (exp>30) {
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fl *= (double) (1L << 30);
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exp -= 30;
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}
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fl *= (double) (1L << exp);
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}
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else {
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/* number need not be normalized */
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if (exp < DBL_MIN_EXP - DBL_MANT_DIG) {
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return 0.0;
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}
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while (exp<-30) {
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fl /= (double) (1L << 30);
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exp += 30;
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}
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fl /= (double) (1L << -exp);
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}
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return sign * fl;
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}
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