0,0 → 1,80 |
/* Copyright (C) 1994 DJ Delorie, see COPYING.DJ for details */ |
/* @(#)s_nextafter.c 5.1 93/09/24 */ |
/* |
* ==================================================== |
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
* |
* Developed at SunPro, a Sun Microsystems, Inc. business. |
* Permission to use, copy, modify, and distribute this |
* software is freely granted, provided that this notice |
* is preserved. |
* ==================================================== |
*/ |
|
#if defined(LIBM_SCCS) && !defined(lint) |
static char rcsid[] = "$Id: s_nextafter.c,v 1.6 1994/08/18 23:07:13 jtc Exp $"; |
#endif |
|
/* IEEE functions |
* nextafter(x,y) |
* return the next machine floating-point number of x in the |
* direction toward y. |
* Special cases: |
*/ |
|
#include "math.h" |
#include "math_private.h" |
|
#ifdef __STDC__ |
double nextafter(double x, double y) |
#else |
double nextafter(x,y) |
double x,y; |
#endif |
{ |
int32_t hx,hy,ix,iy; |
u_int32_t lx,ly; |
|
EXTRACT_WORDS(hx,lx,x); |
EXTRACT_WORDS(hy,ly,y); |
ix = hx&0x7fffffff; /* |x| */ |
iy = hy&0x7fffffff; /* |y| */ |
|
if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */ |
((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0)) /* y is nan */ |
return x+y; |
if(x==y) return x; /* x=y, return x */ |
if((ix|lx)==0) { /* x == 0 */ |
INSERT_WORDS(x,hy&0x80000000,1); /* return +-minsubnormal */ |
y = x*x; |
if(y==x) return y; else return x; /* raise underflow flag */ |
} |
if(hx>=0) { /* x > 0 */ |
if(hx>hy||((hx==hy)&&(lx>ly))) { /* x > y, x -= ulp */ |
if(lx==0) hx -= 1; |
lx -= 1; |
} else { /* x < y, x += ulp */ |
lx += 1; |
if(lx==0) hx += 1; |
} |
} else { /* x < 0 */ |
if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */ |
if(lx==0) hx -= 1; |
lx -= 1; |
} else { /* x > y, x += ulp */ |
lx += 1; |
if(lx==0) hx += 1; |
} |
} |
hy = hx&0x7ff00000; |
if(hy>=0x7ff00000) return x+x; /* overflow */ |
if(hy<0x00100000) { /* underflow */ |
y = x*x; |
if(y!=x) { /* raise underflow flag */ |
INSERT_WORDS(y,hx,lx); |
return y; |
} |
} |
INSERT_WORDS(x,hx,lx); |
return x; |
} |