72 lines
1.1 KiB
C
72 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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* Author: Ceriel J.H. Jacobs
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*/
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/* $Id$ */
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#define __NO_DEFS
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#include <math.h>
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#define NITER 5
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static double
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ldexp(fl,exp)
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double fl;
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int exp;
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{
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extern double _fef();
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int sign = 1;
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int currexp;
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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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fl = _fef(fl,&currexp);
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exp += currexp;
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if (exp > 0) {
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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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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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double
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_sqt(x)
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double x;
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{
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extern double _fef();
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int exponent;
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double val;
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if (x <= 0) {
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if (x < 0) error(3);
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return 0;
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}
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val = _fef(x, &exponent);
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if (exponent & 1) {
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exponent--;
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val *= 2;
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}
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val = ldexp(val + 1.0, exponent/2 - 1);
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/* was: val = (val + 1.0)/2.0; val = ldexp(val, exponent/2); */
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for (exponent = NITER - 1; exponent >= 0; exponent--) {
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val = (val + x / val) / 2.0;
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}
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return val;
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}
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