87 lines
2.2 KiB
C
87 lines
2.2 KiB
C
/* @(#)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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/* IEEE functions
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* nexttoward(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 <float.h>
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#include <openlibm_math.h>
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#include "math_private.h"
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double
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nexttoward(double x, long double y)
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{
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int32_t hx,ix,iy;
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u_int32_t lx,hy,ly,esy;
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EXTRACT_WORDS(hx,lx,x);
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GET_LDOUBLE_WORDS(esy,hy,ly,y);
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ix = hx&0x7fffffff; /* |x| */
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iy = esy&0x7fff; /* |y| */
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if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */
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((iy>=0x7fff)&&(hy|ly)!=0)) /* y is nan */
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return x+y;
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if((long double) x==y) return y; /* x=y, return y */
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if((ix|lx)==0) { /* x == 0 */
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volatile double u;
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INSERT_WORDS(x,(esy&0x8000)<<16,1); /* return +-minsub */
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u = x;
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u = u * u; /* raise underflow flag */
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return x;
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}
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if(hx>=0) { /* x > 0 */
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if (esy>=0x8000||((ix>>20)&0x7ff)>iy-0x3c00
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|| (((ix>>20)&0x7ff)==iy-0x3c00
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&& (((hx<<11)|(lx>>21))>(hy&0x7fffffff)
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|| (((hx<<11)|(lx>>21))==(hy&0x7fffffff)
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&& (lx<<11)>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 (esy<0x8000||((ix>>20)&0x7ff)>iy-0x3c00
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|| (((ix>>20)&0x7ff)==iy-0x3c00
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&& (((hx<<11)|(lx>>21))>(hy&0x7fffffff)
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|| (((hx<<11)|(lx>>21))==(hy&0x7fffffff)
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&& (lx<<11)>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) {
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x = x+x; /* overflow */
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return x;
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}
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if(hy<0x00100000) {
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volatile double u = x*x; /* underflow */
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if(u==x) {
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INSERT_WORDS(x,hx,lx);
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return x;
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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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