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