40 lines
643 B
C
40 lines
643 B
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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* Author: Ceriel J.H. Jacobs
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*/
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/* $Header$ */
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#include <math.h>
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#include <errno.h>
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extern int errno;
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double
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pow(x,y)
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double x,y;
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{
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double dummy;
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extern double modf(), exp(), log();
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if ((x == 0 && y == 0) ||
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(x < 0 && modf(y, &dummy) != 0)) {
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errno = EDOM;
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return 0;
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}
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if (x == 0) return x;
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if (x < 0) {
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double val = exp(log(-x) * y);
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if (modf(y/2.0, &dummy) != 0) {
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/* y was odd */
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val = - val;
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}
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return val;
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}
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return exp(log(x) * y);
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}
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