104 lines
1.9 KiB
C
104 lines
1.9 KiB
C
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/*
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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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#ifndef NOFLOAT
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#include <ctype.h>
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#include <limits.h>
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#include <math.h>
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#include <stdlib.h>
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#define MAX (LONG_MAX/10)
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double
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strtod(register const char *p, register char **pp)
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{
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register int c;
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int exp = 0, sign = 1, expsign = 0;
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double fl;
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long lowl = 0, highl = 0, pos = 1;
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int dotseen = 0;
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int digit_seen = 0;
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if (pp) *pp = p;
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while (isspace(*p)) p++;
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c = *p;
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switch (c) {
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case '-':
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sign = -1;
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/* fallthrough */
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case '+':
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p++;
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}
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while (isdigit(c = *p++) || (c == '.' && ! dotseen++)) {
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if (c == '.') continue;
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digit_seen = 1;
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if (highl < MAX) {
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highl = (highl << 3) + (highl << 1) + (c - '0');
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}
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else if (pos < MAX) {
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pos = (pos << 3) + (pos << 1);
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lowl = (lowl << 3) + (lowl << 1) + (c - '0');
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}
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else exp++;
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if (dotseen) exp--;
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}
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if (! digit_seen) return 0.0;
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fl = highl;
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if (pos > 1) {
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fl = pos * fl + lowl;
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}
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if (pp) *pp = p-1;
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if (c == 'E' || c == 'e') {
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int exp1 = 0;
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int sign = 1;
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switch (*p) {
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case '-':
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sign = -1;
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/* fallthrough */
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case '+':
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p++;
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}
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if (isdigit(c = *p)) {
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do {
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exp1 = 10 * exp1 + c - '0';
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} while (isdigit(c = *++p));
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if (pp) *pp = p;
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}
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exp += sign * exp1;
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}
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if (fl == 0.0) return 0.0;
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if (exp < 0) {
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expsign = 1;
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exp = -exp;
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}
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if (exp != 0) {
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int oldexp = exp;
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double exp5 = 5.0;
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double correction = 1.0;
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while (exp) {
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if (exp % 2) correction *= exp5;
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exp /= 2;
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if (exp != 0) exp5 *= exp5;
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}
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if (expsign) fl = fl / correction;
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else fl = fl * correction;
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fl = ldexp(fl, expsign ? -oldexp : oldexp);
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}
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return sign * fl;
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}
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#endif
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