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 1.10 1999/07/02 15:37:43 simonb 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 #ifdef __STDC__ 29 double nextafter(double x, double y) 30 #else 31 double nextafter(x,y) 32 double x,y; 33 #endif 34 { 35 int32_t hx,hy,ix,iy; 36 u_int32_t lx,ly; 37 38 EXTRACT_WORDS(hx,lx,x); 39 EXTRACT_WORDS(hy,ly,y); 40 ix = hx&0x7fffffff; /* |x| */ 41 iy = hy&0x7fffffff; /* |y| */ 42 43 if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */ 44 ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0)) /* y is nan */ 45 return x+y; 46 if(x==y) return x; /* x=y, return x */ 47 if((ix|lx)==0) { /* x == 0 */ 48 INSERT_WORDS(x,hy&0x80000000,1); /* return +-minsubnormal */ 49 y = x*x; 50 if(y==x) return y; else return x; /* raise underflow flag */ 51 } 52 if(hx>=0) { /* x > 0 */ 53 if(hx>hy||((hx==hy)&&(lx>ly))) { /* x > y, x -= ulp */ 54 if(lx==0) hx -= 1; 55 lx -= 1; 56 } else { /* x < y, x += ulp */ 57 lx += 1; 58 if(lx==0) hx += 1; 59 } 60 } else { /* x < 0 */ 61 if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */ 62 if(lx==0) hx -= 1; 63 lx -= 1; 64 } else { /* x > y, x += ulp */ 65 lx += 1; 66 if(lx==0) hx += 1; 67 } 68 } 69 hy = hx&0x7ff00000; 70 if(hy>=0x7ff00000) return x+x; /* overflow */ 71 if(hy<0x00100000) { /* underflow */ 72 y = x*x; 73 if(y!=x) { /* raise underflow flag */ 74 INSERT_WORDS(y,hx,lx); 75 return y; 76 } 77 } 78 INSERT_WORDS(x,hx,lx); 79 return x; 80 } 81