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 1.16 2017/08/16 11:22:52 he 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 #endif 32 33 double 34 nextafter(double x, double y) 35 { 36 int32_t hx,hy,ix,iy; 37 u_int32_t lx,ly; 38 39 EXTRACT_WORDS(hx,lx,x); 40 EXTRACT_WORDS(hy,ly,y); 41 ix = hx&0x7fffffff; /* |x| */ 42 iy = hy&0x7fffffff; /* |y| */ 43 44 if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */ 45 ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0)) /* y is nan */ 46 return x+y; 47 if(x==y) return y; /* x=y, return y */ 48 if((ix|lx)==0) { /* x == 0 */ 49 INSERT_WORDS(x,hy&0x80000000,1); /* return +-minsubnormal */ 50 y = x*x; 51 if(y==x) return y; else return x; /* raise underflow flag */ 52 } 53 if(hx>=0) { /* x > 0 */ 54 if(hx>hy||((hx==hy)&&(lx>ly))) { /* x > y, x -= ulp */ 55 if(lx==0) hx -= 1; 56 lx -= 1; 57 } else { /* x < y, x += ulp */ 58 lx += 1; 59 if(lx==0) hx += 1; 60 } 61 } else { /* x < 0 */ 62 if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */ 63 if(lx==0) hx -= 1; 64 lx -= 1; 65 } else { /* x > y, x += ulp */ 66 lx += 1; 67 if(lx==0) hx += 1; 68 } 69 } 70 hy = hx&0x7ff00000; 71 if(hy>=0x7ff00000) return x+x; /* overflow */ 72 if(hy<0x00100000) { /* underflow */ 73 y = x*x; 74 if(y!=x) { /* raise underflow flag */ 75 INSERT_WORDS(y,hx,lx); 76 return y; 77 } 78 } 79 INSERT_WORDS(x,hx,lx); 80 return x; 81 } 82