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 <float.h> 21 #include <math.h> 22 23 #include "math_private.h" 24 25 double 26 nextafter(double x, double y) 27 { 28 int32_t hx,hy,ix,iy; 29 u_int32_t lx,ly; 30 31 EXTRACT_WORDS(hx,lx,x); 32 EXTRACT_WORDS(hy,ly,y); 33 ix = hx&0x7fffffff; /* |x| */ 34 iy = hy&0x7fffffff; /* |y| */ 35 36 if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */ 37 ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0)) /* y is nan */ 38 return x+y; 39 if(x==y) return y; /* x=y, return y */ 40 if((ix|lx)==0) { /* x == 0 */ 41 INSERT_WORDS(x,hy&0x80000000,1); /* return +-minsubnormal */ 42 y = x*x; 43 if(y==x) return y; else return x; /* raise underflow flag */ 44 } 45 if(hx>=0) { /* x > 0 */ 46 if(hx>hy||((hx==hy)&&(lx>ly))) { /* x > y, x -= ulp */ 47 if(lx==0) hx -= 1; 48 lx -= 1; 49 } else { /* x < y, x += ulp */ 50 lx += 1; 51 if(lx==0) hx += 1; 52 } 53 } else { /* x < 0 */ 54 if(hy>=0||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 } 62 hy = hx&0x7ff00000; 63 if(hy>=0x7ff00000) return x+x; /* overflow */ 64 if(hy<0x00100000) { /* underflow */ 65 y = x*x; 66 if(y!=x) { /* raise underflow flag */ 67 INSERT_WORDS(y,hx,lx); 68 return y; 69 } 70 } 71 INSERT_WORDS(x,hx,lx); 72 return x; 73 } 74 75 #if LDBL_MANT_DIG == DBL_MANT_DIG 76 __strong_alias(nextafterl, nextafter); 77 __strong_alias(nexttoward, nextafter); 78 __strong_alias(nexttowardl, nextafter); 79 #endif /* LDBL_MANT_DIG == DBL_MANT_DIG */ 80