1*1e651e1eSRoland Levillain 2*1e651e1eSRoland Levillain /* @(#)s_nextafter.c 1.3 95/01/18 */ 3*1e651e1eSRoland Levillain /* 4*1e651e1eSRoland Levillain * ==================================================== 5*1e651e1eSRoland Levillain * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 6*1e651e1eSRoland Levillain * 7*1e651e1eSRoland Levillain * Developed at SunSoft, a Sun Microsystems, Inc. business. 8*1e651e1eSRoland Levillain * Permission to use, copy, modify, and distribute this 9*1e651e1eSRoland Levillain * software is freely granted, provided that this notice 10*1e651e1eSRoland Levillain * is preserved. 11*1e651e1eSRoland Levillain * ==================================================== 12*1e651e1eSRoland Levillain */ 13*1e651e1eSRoland Levillain 14*1e651e1eSRoland Levillain /* IEEE functions 15*1e651e1eSRoland Levillain * nextafter(x,y) 16*1e651e1eSRoland Levillain * return the next machine floating-point number of x in the 17*1e651e1eSRoland Levillain * direction toward y. 18*1e651e1eSRoland Levillain * Special cases: 19*1e651e1eSRoland Levillain */ 20*1e651e1eSRoland Levillain 21*1e651e1eSRoland Levillain #include "fdlibm.h" 22*1e651e1eSRoland Levillain 23*1e651e1eSRoland Levillain #ifdef __STDC__ ieee_nextafter(double x,double y)24*1e651e1eSRoland Levillain double ieee_nextafter(double x, double y) 25*1e651e1eSRoland Levillain #else 26*1e651e1eSRoland Levillain double ieee_nextafter(x,y) 27*1e651e1eSRoland Levillain double x,y; 28*1e651e1eSRoland Levillain #endif 29*1e651e1eSRoland Levillain { 30*1e651e1eSRoland Levillain int hx,hy,ix,iy; 31*1e651e1eSRoland Levillain unsigned lx,ly; 32*1e651e1eSRoland Levillain 33*1e651e1eSRoland Levillain hx = __HI(x); /* high word of x */ 34*1e651e1eSRoland Levillain lx = __LO(x); /* low word of x */ 35*1e651e1eSRoland Levillain hy = __HI(y); /* high word of y */ 36*1e651e1eSRoland Levillain ly = __LO(y); /* low word of y */ 37*1e651e1eSRoland Levillain ix = hx&0x7fffffff; /* |x| */ 38*1e651e1eSRoland Levillain iy = hy&0x7fffffff; /* |y| */ 39*1e651e1eSRoland Levillain 40*1e651e1eSRoland Levillain if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */ 41*1e651e1eSRoland Levillain ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0)) /* y is nan */ 42*1e651e1eSRoland Levillain return x+y; 43*1e651e1eSRoland Levillain if(x==y) return x; /* x=y, return x */ 44*1e651e1eSRoland Levillain if((ix|lx)==0) { /* x == 0 */ 45*1e651e1eSRoland Levillain __HI(x) = hy&0x80000000; /* return +-minsubnormal */ 46*1e651e1eSRoland Levillain __LO(x) = 1; 47*1e651e1eSRoland Levillain y = x*x; 48*1e651e1eSRoland Levillain if(y==x) return y; else return x; /* raise underflow flag */ 49*1e651e1eSRoland Levillain } 50*1e651e1eSRoland Levillain if(hx>=0) { /* x > 0 */ 51*1e651e1eSRoland Levillain if(hx>hy||((hx==hy)&&(lx>ly))) { /* x > y, x -= ulp */ 52*1e651e1eSRoland Levillain if(lx==0) hx -= 1; 53*1e651e1eSRoland Levillain lx -= 1; 54*1e651e1eSRoland Levillain } else { /* x < y, x += ulp */ 55*1e651e1eSRoland Levillain lx += 1; 56*1e651e1eSRoland Levillain if(lx==0) hx += 1; 57*1e651e1eSRoland Levillain } 58*1e651e1eSRoland Levillain } else { /* x < 0 */ 59*1e651e1eSRoland Levillain if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */ 60*1e651e1eSRoland Levillain if(lx==0) hx -= 1; 61*1e651e1eSRoland Levillain lx -= 1; 62*1e651e1eSRoland Levillain } else { /* x > y, x += ulp */ 63*1e651e1eSRoland Levillain lx += 1; 64*1e651e1eSRoland Levillain if(lx==0) hx += 1; 65*1e651e1eSRoland Levillain } 66*1e651e1eSRoland Levillain } 67*1e651e1eSRoland Levillain hy = hx&0x7ff00000; 68*1e651e1eSRoland Levillain if(hy>=0x7ff00000) return x+x; /* overflow */ 69*1e651e1eSRoland Levillain if(hy<0x00100000) { /* underflow */ 70*1e651e1eSRoland Levillain y = x*x; 71*1e651e1eSRoland Levillain if(y!=x) { /* raise underflow flag */ 72*1e651e1eSRoland Levillain __HI(y) = hx; __LO(y) = lx; 73*1e651e1eSRoland Levillain return y; 74*1e651e1eSRoland Levillain } 75*1e651e1eSRoland Levillain } 76*1e651e1eSRoland Levillain __HI(x) = hx; __LO(x) = lx; 77*1e651e1eSRoland Levillain return x; 78*1e651e1eSRoland Levillain } 79