1 /* @(#)s_nextafter.c 5.1 93/09/24 */ 2 /* 3 * ==================================================== 4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 5 * 6 * Developed at SunPro, a Sun Microsystems, Inc. business. 7 * Permission to use, copy, modify, and distribute this 8 * software is freely granted, provided that this notice 9 * is preserved. 10 * ==================================================== 11 */ 12 13 #include <sys/cdefs.h> 14 #if defined(LIBM_SCCS) && !defined(lint) 15 __RCSID("$NetBSD: s_nextafter.c,v 1.11 2002/05/26 22:01:57 wiz Exp $"); 16 #endif 17 18 /* IEEE functions 19 * nextafter(x,y) 20 * return the next machine floating-point number of x in the 21 * direction toward y. 22 * Special cases: 23 */ 24 25 #include "math.h" 26 #include "math_private.h" 27 28 double 29 nextafter(double x, double y) 30 { 31 int32_t hx,hy,ix,iy; 32 u_int32_t lx,ly; 33 34 EXTRACT_WORDS(hx,lx,x); 35 EXTRACT_WORDS(hy,ly,y); 36 ix = hx&0x7fffffff; /* |x| */ 37 iy = hy&0x7fffffff; /* |y| */ 38 39 if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */ 40 ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0)) /* y is nan */ 41 return x+y; 42 if(x==y) return x; /* x=y, return x */ 43 if((ix|lx)==0) { /* x == 0 */ 44 INSERT_WORDS(x,hy&0x80000000,1); /* return +-minsubnormal */ 45 y = x*x; 46 if(y==x) return y; else return x; /* raise underflow flag */ 47 } 48 if(hx>=0) { /* x > 0 */ 49 if(hx>hy||((hx==hy)&&(lx>ly))) { /* x > y, x -= ulp */ 50 if(lx==0) hx -= 1; 51 lx -= 1; 52 } else { /* x < y, x += ulp */ 53 lx += 1; 54 if(lx==0) hx += 1; 55 } 56 } else { /* x < 0 */ 57 if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */ 58 if(lx==0) hx -= 1; 59 lx -= 1; 60 } else { /* x > y, x += ulp */ 61 lx += 1; 62 if(lx==0) hx += 1; 63 } 64 } 65 hy = hx&0x7ff00000; 66 if(hy>=0x7ff00000) return x+x; /* overflow */ 67 if(hy<0x00100000) { /* underflow */ 68 y = x*x; 69 if(y!=x) { /* raise underflow flag */ 70 INSERT_WORDS(y,hx,lx); 71 return y; 72 } 73 } 74 INSERT_WORDS(x,hx,lx); 75 return x; 76 } 77