ref: a39ae178fcc4387fe63efea4d15b34d52f4a13de
dir: /libmath/fdlibm/s_nextafter.c/
/* derived from /netlib/fdlibm */
/* @(#)s_nextafter.c 1.3 95/01/18 */
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunSoft, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
/* IEEE functions
* nextafter(x,y)
* return the next machine floating-point number of x in the
* direction toward y.
* Special cases:
*/
#include "fdlibm.h"
double nextafter(double x, double y)
{
int hx,hy,ix,iy;
unsigned lx,ly;
hx = __HI(x); /* high word of x */
lx = __LO(x); /* low word of x */
hy = __HI(y); /* high word of y */
ly = __LO(y); /* low word of 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 */
__HI(x) = hy&0x80000000; /* return +-minsubnormal */
__LO(x) = 1;
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 */
__HI(y) = hx; __LO(y) = lx;
return y;
}
}
__HI(x) = hx; __LO(x) = lx;
return x;
}