ref: 53aac62a54ebbcc1781c0000d3e2384ed038c7bb
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; }