114 lines
2.4 KiB
C
114 lines
2.4 KiB
C
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/* @(#)e_remainder.c 5.1 93/09/24 */
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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/*
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FUNCTION
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<<remainder>>, <<remainderf>>---round and remainder
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INDEX
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remainder
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INDEX
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remainderf
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ANSI_SYNOPSIS
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#include <math.h>
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double remainder(double <[x]>, double <[y]>);
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float remainderf(float <[x]>, float <[y]>);
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TRAD_SYNOPSIS
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#include <math.h>
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double remainder(<[x]>,<[y]>)
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double <[x]>, <[y]>;
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float remainderf(<[x]>,<[y]>)
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float <[x]>, <[y]>;
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DESCRIPTION
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<<remainder>> and <<remainderf>> find the remainder of
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<[x]>/<[y]>; this value is in the range -<[y]>/2 .. +<[y]>/2.
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RETURNS
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<<remainder>> returns the integer result as a double.
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PORTABILITY
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<<remainder>> is a System V release 4.
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<<remainderf>> is an extension.
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*/
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/* remainder(x,p)
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* Return :
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* returns x REM p = x - [x/p]*p as if in infinite
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* precise arithmetic, where [x/p] is the (infinite bit)
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* integer nearest x/p (in half way case choose the even one).
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* Method :
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* Based on fmod() return x-[x/p]chopped*p exactlp.
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*/
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#include "fdlibm.h"
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#ifndef _DOUBLE_IS_32BITS
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#ifdef __STDC__
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static const double zero = 0.0;
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#else
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static double zero = 0.0;
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#endif
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#ifdef __STDC__
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double remainder(double x, double p)
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#else
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double remainder(x,p)
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double x,p;
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#endif
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{
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__int32_t hx,hp;
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__uint32_t sx,lx,lp;
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double p_half;
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EXTRACT_WORDS(hx,lx,x);
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EXTRACT_WORDS(hp,lp,p);
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sx = hx&0x80000000;
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hp &= 0x7fffffff;
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hx &= 0x7fffffff;
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/* purge off exception values */
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if((hp|lp)==0) return (x*p)/(x*p); /* p = 0 */
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if((hx>=0x7ff00000)|| /* x not finite */
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((hp>=0x7ff00000)&& /* p is NaN */
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(((hp-0x7ff00000)|lp)!=0)))
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return (x*p)/(x*p);
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if (hp<=0x7fdfffff) x = fmod(x,p+p); /* now x < 2p */
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if (((hx-hp)|(lx-lp))==0) return zero*x;
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x = fabs(x);
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p = fabs(p);
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if (hp<0x00200000) {
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if(x+x>p) {
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x-=p;
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if(x+x>=p) x -= p;
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}
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} else {
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p_half = 0.5*p;
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if(x>p_half) {
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x-=p;
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if(x>=p_half) x -= p;
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}
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}
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GET_HIGH_WORD(hx,x);
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SET_HIGH_WORD(x,hx^sx);
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return x;
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}
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#endif /* defined(_DOUBLE_IS_32BITS) */
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