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110 lines
2.7 KiB
C
110 lines
2.7 KiB
C
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/* @(#)s_nextafter.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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<<nextafter>>, <<nextafterf>>---get next number
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INDEX
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nextafter
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INDEX
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nextafterf
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SYNOPSIS
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#include <math.h>
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double nextafter(double <[val]>, double <[dir]>);
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float nextafterf(float <[val]>, float <[dir]>);
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DESCRIPTION
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<<nextafter>> returns the double-precision floating-point number
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closest to <[val]> in the direction toward <[dir]>. <<nextafterf>>
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performs the same operation in single precision. For example,
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<<nextafter(0.0,1.0)>> returns the smallest positive number which is
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representable in double precision.
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RETURNS
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Returns the next closest number to <[val]> in the direction toward
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<[dir]>.
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PORTABILITY
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Neither <<nextafter>> nor <<nextafterf>> is required by ANSI C
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or by the System V Interface Definition (Issue 2).
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*/
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/* IEEE functions
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* nextafter(x,y)
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* return the next machine floating-point number of x in the
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* direction toward y.
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* Special cases:
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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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double nextafter(double x, double y)
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#else
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double nextafter(x,y)
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double x,y;
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#endif
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{
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__int32_t hx,hy,ix,iy;
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__uint32_t lx,ly;
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EXTRACT_WORDS(hx,lx,x);
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EXTRACT_WORDS(hy,ly,y);
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ix = hx&0x7fffffff; /* |x| */
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iy = hy&0x7fffffff; /* |y| */
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if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */
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((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0)) /* y is nan */
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return x+y;
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if(x==y) return x; /* x=y, return x */
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if((ix|lx)==0) { /* x == 0 */
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INSERT_WORDS(x,hy&0x80000000,1); /* return +-minsubnormal */
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y = x*x;
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if(y==x) return y; else return x; /* raise underflow flag */
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}
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if(hx>=0) { /* x > 0 */
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if(hx>hy||((hx==hy)&&(lx>ly))) { /* x > y, x -= ulp */
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if(lx==0) hx -= 1;
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lx -= 1;
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} else { /* x < y, x += ulp */
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lx += 1;
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if(lx==0) hx += 1;
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}
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} else { /* x < 0 */
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if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */
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if(lx==0) hx -= 1;
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lx -= 1;
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} else { /* x > y, x += ulp */
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lx += 1;
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if(lx==0) hx += 1;
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}
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}
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hy = hx&0x7ff00000;
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if(hy>=0x7ff00000) return x+x; /* overflow */
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if(hy<0x00100000) { /* underflow */
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y = x*x;
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if(y!=x) { /* raise underflow flag */
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INSERT_WORDS(y,hx,lx);
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return y;
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}
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}
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INSERT_WORDS(x,hx,lx);
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return x;
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}
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#endif /* _DOUBLE_IS_32BITS */
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