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/* @(#)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.
* ====================================================
*/
/*
FUNCTION
<<nextafter>>, <<nextafterf>>---get next number
INDEX
nextafter
INDEX
nextafterf
ANSI_SYNOPSIS
#include <math.h>
double nextafter(double <[val]>, double <[dir]>);
float nextafterf(float <[val]>, float <[dir]>);
TRAD_SYNOPSIS
#include <math.h>
double nextafter(<[val]>, <[dir]>)
double <[val]>;
double <[exp]>;
float nextafter(<[val]>, <[dir]>)
float <[val]>;
float <[dir]>;
DESCRIPTION
<<nextafter>> returns the double-precision floating-point number
closest to <[val]> in the direction toward <[dir]>. <<nextafterf>>
performs the same operation in single precision. For example,
<<nextafter(0.0,1.0)>> returns the smallest positive number which is
representable in double precision.
RETURNS
Returns the next closest number to <[val]> in the direction toward
<[dir]>.
PORTABILITY
Neither <<nextafter>> nor <<nextafterf>> is required by ANSI C
or by the System V Interface Definition (Issue 2).
*/
/* IEEE functions
* nextafter(x,y)
* return the next machine floating-point number of x in the
* direction toward y.
* Special cases:
*/
#include "fdlibm.h"
#ifndef _DOUBLE_IS_32BITS
#ifdef __STDC__
double nextafter(double x, double y)
#else
double nextafter(x,y)
double x,y;
#endif
{
__int32_t hx,hy,ix,iy;
__uint32_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;
}
#endif /* _DOUBLE_IS_32BITS */
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