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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 2 | pj | 1 | /* @(#)s_nextafter.c 5.1 93/09/24 */ |
| 2 | /* |
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| 3 | * ==================================================== |
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| 4 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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| 5 | * |
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| 6 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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| 7 | * Permission to use, copy, modify, and distribute this |
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| 8 | * software is freely granted, provided that this notice |
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| 9 | * is preserved. |
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| 10 | * ==================================================== |
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| 11 | */ |
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| 12 | |||
| 13 | #ifndef lint |
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| 14 | static char rcsid[] = "$\Id: s_nextafter.c,v 1.2 1995/05/30 05:50:11 rgrimes Exp $"; |
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| 15 | #endif |
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| 16 | |||
| 17 | /* IEEE functions |
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| 18 | * nextafter(x,y) |
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| 19 | * return the next machine floating-point number of x in the |
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| 20 | * direction toward y. |
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| 21 | * Special cases: |
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| 22 | */ |
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| 23 | |||
| 24 | #include "math.h" |
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| 25 | #include "math_private.h" |
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| 26 | |||
| 27 | #ifdef __STDC__ |
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| 28 | double nextafter(double x, double y) |
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| 29 | #else |
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| 30 | double nextafter(x,y) |
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| 31 | double x,y; |
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| 32 | #endif |
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| 33 | { |
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| 34 | int32_t hx,hy,ix,iy; |
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| 35 | u_int32_t lx,ly; |
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| 36 | |||
| 37 | EXTRACT_WORDS(hx,lx,x); |
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| 38 | EXTRACT_WORDS(hy,ly,y); |
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| 39 | ix = hx&0x7fffffff; /* |x| */ |
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| 40 | iy = hy&0x7fffffff; /* |y| */ |
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| 41 | |||
| 42 | if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */ |
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| 43 | ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0)) /* y is nan */ |
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| 44 | return x+y; |
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| 45 | if(x==y) return x; /* x=y, return x */ |
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| 46 | if((ix|lx)==0) { /* x == 0 */ |
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| 47 | INSERT_WORDS(x,hy&0x80000000,1); /* return +-minsubnormal */ |
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| 48 | y = x*x; |
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| 49 | if(y==x) return y; else return x; /* raise underflow flag */ |
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| 50 | } |
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| 51 | if(hx>=0) { /* x > 0 */ |
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| 52 | if(hx>hy||((hx==hy)&&(lx>ly))) { /* x > y, x -= ulp */ |
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| 53 | if(lx==0) hx -= 1; |
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| 54 | lx -= 1; |
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| 55 | } else { /* x < y, x += ulp */ |
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| 56 | lx += 1; |
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| 57 | if(lx==0) hx += 1; |
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| 58 | } |
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| 59 | } else { /* x < 0 */ |
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| 60 | if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */ |
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| 61 | if(lx==0) hx -= 1; |
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| 62 | lx -= 1; |
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| 63 | } else { /* x > y, x += ulp */ |
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| 64 | lx += 1; |
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| 65 | if(lx==0) hx += 1; |
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| 66 | } |
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| 67 | } |
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| 68 | hy = hx&0x7ff00000; |
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| 69 | if(hy>=0x7ff00000) return x+x; /* overflow */ |
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| 70 | if(hy<0x00100000) { /* underflow */ |
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| 71 | y = x*x; |
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| 72 | if(y!=x) { /* raise underflow flag */ |
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| 73 | INSERT_WORDS(y,hx,lx); |
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| 74 | return y; |
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| 75 | } |
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| 76 | } |
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| 77 | INSERT_WORDS(x,hx,lx); |
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| 78 | return x; |
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| 79 | } |