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 #ifndef lint 14 static char rcsid[] = "$FreeBSD$"; 15 #endif 16 17 /* IEEE functions 18 * nextafter(x,y) 19 * return the next machine floating-point number of x in the 20 * direction toward y. 21 * Special cases: 22 */ 23 24 #include "math.h" 25 #include "math_private.h" 26 27 #ifdef __STDC__ 28 double nextafter(double x, double y) 29 #else 30 double nextafter(x,y) 31 double x,y; 32 #endif 33 { 34 int32_t hx,hy,ix,iy; 35 u_int32_t lx,ly; 36 37 EXTRACT_WORDS(hx,lx,x); 38 EXTRACT_WORDS(hy,ly,y); 39 ix = hx&0x7fffffff; /* |x| */ 40 iy = hy&0x7fffffff; /* |y| */ 41 42 if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */ 43 ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0)) /* y is nan */ 44 return x+y; 45 if(x==y) return x; /* x=y, return x */ 46 if((ix|lx)==0) { /* x == 0 */ 47 INSERT_WORDS(x,hy&0x80000000,1); /* return +-minsubnormal */ 48 y = x*x; 49 if(y==x) return y; else return x; /* raise underflow flag */ 50 } 51 if(hx>=0) { /* x > 0 */ 52 if(hx>hy||((hx==hy)&&(lx>ly))) { /* x > y, x -= ulp */ 53 if(lx==0) hx -= 1; 54 lx -= 1; 55 } else { /* x < y, x += ulp */ 56 lx += 1; 57 if(lx==0) hx += 1; 58 } 59 } else { /* x < 0 */ 60 if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */ 61 if(lx==0) hx -= 1; 62 lx -= 1; 63 } else { /* x > y, x += ulp */ 64 lx += 1; 65 if(lx==0) hx += 1; 66 } 67 } 68 hy = hx&0x7ff00000; 69 if(hy>=0x7ff00000) return x+x; /* overflow */ 70 if(hy<0x00100000) { /* underflow */ 71 y = x*x; 72 if(y!=x) { /* raise underflow flag */ 73 INSERT_WORDS(y,hx,lx); 74 return y; 75 } 76 } 77 INSERT_WORDS(x,hx,lx); 78 return x; 79 } 80