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56 lines
1.3 KiB
56 lines
1.3 KiB
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/* @(#)s_frexp.c 1.4 95/01/18 */ |
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/* |
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* ==================================================== |
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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* |
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* Developed at SunSoft, a Sun Microsystems, Inc. business. |
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* Permission to use, copy, modify, and distribute this |
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* software is freely granted, provided that this notice |
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* is preserved. |
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* ==================================================== |
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*/ |
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/* |
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* for non-zero x |
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* x = ieee_frexp(arg,&exp); |
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* return a double fp quantity x such that 0.5 <= |x| <1.0 |
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* and the corresponding binary exponent "exp". That is |
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* arg = x*2^exp. |
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* If arg is inf, 0.0, or NaN, then ieee_frexp(arg,&exp) returns arg |
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* with *exp=0. |
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*/ |
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#include "fdlibm.h" |
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#ifdef __STDC__ |
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static const double |
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#else |
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static double |
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#endif |
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two54 = 1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */ |
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#ifdef __STDC__ |
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double ieee_frexp(double x, int *eptr) |
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#else |
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double ieee_frexp(x, eptr) |
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double x; int *eptr; |
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#endif |
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{ |
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int hx, ix, lx; |
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hx = __HI(x); |
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ix = 0x7fffffff&hx; |
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lx = __LO(x); |
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*eptr = 0; |
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if(ix>=0x7ff00000||((ix|lx)==0)) return x; /* 0,inf,nan */ |
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if (ix<0x00100000) { /* subnormal */ |
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x *= two54; |
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hx = __HI(x); |
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ix = hx&0x7fffffff; |
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*eptr = -54; |
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} |
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*eptr += (ix>>20)-1022; |
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hx = (hx&0x800fffff)|0x3fe00000; |
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__HI(x) = hx; |
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return x; |
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}
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