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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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/* 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 <math.h> |
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#include <float.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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} |