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 1.17 2024/05/05 22:10:06 riastradh 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#ifndef __HAVE_LONG_DOUBLE 29__strong_alias(nextafterl, nextafter) 30__strong_alias(nexttoward, nextafter) 31__strong_alias(nexttowardl, nextafter) 32#endif 33 34double 35nextafter(double x, double y) 36{ 37 int32_t hx,hy,ix,iy; 38 u_int32_t lx,ly; 39 40 EXTRACT_WORDS(hx,lx,x); 41 EXTRACT_WORDS(hy,ly,y); 42 ix = hx&0x7fffffff; /* |x| */ 43 iy = hy&0x7fffffff; /* |y| */ 44 45 if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */ 46 ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0)) /* y is nan */ 47 return x+y; 48 if(x==y) return y; /* x=y, return y */ 49 if((ix|lx)==0) { /* x == 0 */ 50 INSERT_WORDS(x,hy&0x80000000,1); /* return +-minsubnormal */ 51 y = x*x; 52 if(y==x) return y; else return x; /* raise underflow flag */ 53 } 54 if(hx>=0) { /* x > 0 */ 55 if(hx>hy||((hx==hy)&&(lx>ly))) { /* x > y, x -= ulp */ 56 if(lx==0) hx -= 1; 57 lx -= 1; 58 } else { /* x < y, x += ulp */ 59 lx += 1; 60 if(lx==0) hx += 1; 61 } 62 } else { /* x < 0 */ 63 if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */ 64 if(lx==0) hx -= 1; 65 lx -= 1; 66 } else { /* x > y, x += ulp */ 67 lx += 1; 68 if(lx==0) hx += 1; 69 } 70 } 71 hy = hx&0x7ff00000; 72 if(hy>=0x7ff00000) return x+x; /* overflow */ 73 if(hy<0x00100000) { /* underflow */ 74 y = x*x; 75 if(y!=x) { /* raise underflow flag */ 76 INSERT_WORDS(y,hx,lx); 77 return y; 78 } 79 } 80 INSERT_WORDS(x,hx,lx); 81 return x; 82} 83