78 lines
1.2 KiB
C
78 lines
1.2 KiB
C
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/*
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* (c) copyright 1983 by the Vrije Universiteit, Amsterdam, The Netherlands.
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*
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* This product is part of the Amsterdam Compiler Kit.
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*
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* Permission to use, sell, duplicate or disclose this software must be
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* obtained in writing. Requests for such permissions may be sent to
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*
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* Dr. Andrew S. Tanenbaum
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* Wiskundig Seminarium
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* Vrije Universiteit
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* Postbox 7161
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* 1007 MC Amsterdam
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* The Netherlands
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*
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*/
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/* Author: J.W. Stevenson */
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#include <pc_err.h>
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extern double _fef();
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extern _trp();
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/*
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sqrt returns the square root of its floating
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point argument. Newton's method.
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calls _fef
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*/
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double
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_sqt(arg)
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double arg;
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{
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double x, temp;
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int exp;
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int i;
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if(arg <= 0) {
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if(arg < 0)
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_trp(ESQT);
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return(0);
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}
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x = _fef(arg,&exp);
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/*
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while(x < 0.5) {
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x =* 2;
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exp--;
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}
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*/
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/*
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* NOTE
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* this wont work on 1's comp
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*/
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if(exp & 1) {
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x *= 2;
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exp--;
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}
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temp = 0.5*(1 + x);
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while(exp > 28) {
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temp *= (1<<14);
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exp -= 28;
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}
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while(exp < -28) {
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temp /= (1<<14);
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exp += 28;
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}
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if(exp >= 0)
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temp *= 1 << (exp/2);
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else
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temp /= 1 << (-exp/2);
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for(i=0; i<=4; i++)
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temp = 0.5*(temp + arg/temp);
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return(temp);
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}
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