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4973 | right-hear | 1 | /* Copyright (C) 1994 DJ Delorie, see COPYING.DJ for details */ |
2 | /* @(#)s_frexp.c 5.1 93/09/24 */ |
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3 | /* |
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4 | * ==================================================== |
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5 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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6 | * |
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7 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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8 | * Permission to use, copy, modify, and distribute this |
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9 | * software is freely granted, provided that this notice |
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10 | * is preserved. |
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11 | * ==================================================== |
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12 | */ |
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13 | |||
14 | #if defined(LIBM_SCCS) && !defined(lint) |
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15 | static char rcsid[] = "$Id: s_frexp.c,v 1.6 1994/08/18 23:06:49 jtc Exp $"; |
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16 | #endif |
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17 | |||
18 | /* |
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19 | * for non-zero x |
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20 | * x = frexp(arg,&exp); |
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21 | * return a double fp quantity x such that 0.5 <= |x| <1.0 |
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22 | * and the corresponding binary exponent "exp". That is |
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23 | * arg = x*2^exp. |
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24 | * If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg |
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25 | * with *exp=0. |
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26 | */ |
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27 | |||
28 | #include "math.h" |
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29 | #include "math_private.h" |
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30 | |||
31 | #ifdef __STDC__ |
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32 | static const double |
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33 | #else |
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34 | static double |
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35 | #endif |
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36 | one = 1.00000000000000000000e+00, /* 0x3FF00000, 0x00000000 */ |
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37 | two54 = 1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */ |
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38 | |||
39 | #ifdef __STDC__ |
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40 | double frexp(double x, int *eptr) |
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41 | #else |
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42 | double frexp(x, eptr) |
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43 | double x; int *eptr; |
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44 | #endif |
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45 | { |
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46 | int32_t hx, ix, lx; |
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47 | EXTRACT_WORDS(hx,lx,x); |
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48 | ix = 0x7fffffff&hx; |
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49 | *eptr = 0; |
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50 | if(ix>=0x7ff00000||((ix|lx)==0)) return x; /* 0,inf,nan */ |
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51 | if (ix<0x00100000) { /* subnormal */ |
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52 | x *= two54; |
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53 | GET_HIGH_WORD(hx,x); |
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54 | ix = hx&0x7fffffff; |
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55 | *eptr = -54; |
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56 | } |
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57 | *eptr += (ix>>20)-1022; |
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58 | hx = (hx&0x800fffff)|0x3fe00000; |
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59 | SET_HIGH_WORD(x,hx); |
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60 | return x; |
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61 | }0x00100000)>1.0 |