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| Rev | Author | Line No. | Line |
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| 2 | pj | 1 | /* @(#)s_frexp.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_frexp.c,v 1.3 1995/05/30 05:49:41 rgrimes Exp $"; |
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| 15 | #endif |
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| 16 | |||
| 17 | /* |
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| 18 | * for non-zero x |
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| 19 | * x = frexp(arg,&exp); |
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| 20 | * return a double fp quantity x such that 0.5 <= |x| <1.0 |
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| 21 | * and the corresponding binary exponent "exp". That is |
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| 22 | * arg = x*2^exp. |
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| 23 | * If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg |
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| 24 | * with *exp=0. |
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| 25 | */ |
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| 26 | |||
| 27 | #include "math.h" |
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| 28 | #include "math_private.h" |
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| 29 | |||
| 30 | #ifdef __STDC__ |
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| 31 | static const double |
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| 32 | #else |
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| 33 | static double |
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| 34 | #endif |
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| 35 | two54 = 1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */ |
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| 36 | |||
| 37 | #ifdef __STDC__ |
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| 38 | double frexp(double x, int *eptr) |
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| 39 | #else |
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| 40 | double frexp(x, eptr) |
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| 41 | double x; int *eptr; |
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| 42 | #endif |
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| 43 | { |
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| 44 | int32_t hx, ix, lx; |
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| 45 | EXTRACT_WORDS(hx,lx,x); |
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| 46 | ix = 0x7fffffff&hx; |
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| 47 | *eptr = 0; |
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| 48 | if(ix>=0x7ff00000||((ix|lx)==0)) return x; /* 0,inf,nan */ |
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| 49 | if (ix<0x00100000) { /* subnormal */ |
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| 50 | x *= two54; |
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| 51 | GET_HIGH_WORD(hx,x); |
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| 52 | ix = hx&0x7fffffff; |
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| 53 | *eptr = -54; |
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| 54 | } |
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| 55 | *eptr += (ix>>20)-1022; |
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| 56 | hx = (hx&0x800fffff)|0x3fe00000; |
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| 57 | SET_HIGH_WORD(x,hx); |
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| 58 | return x; |
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| 59 | } |