mirror of https://github.com/zeldaret/tp.git
59 lines
1.7 KiB
C
59 lines
1.7 KiB
C
/* @(#)s_ldexp.c 1.2 95/01/04 */
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/* $Id: s_ldexp.c,v 1.3.14.1 2002/01/31 15:24:14 ceciliar Exp $ */
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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 SunPro, 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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#include "fdlibm.h"
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#include "MSL_C/math.h" /* for isfinite macro */
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static const double
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two54
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= 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
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twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
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big = 1.0e+300, tiny = 1.0e-300;
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double ldexp(double x, int n)
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{
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long k, hx, lx; /*- cc 020130 -*/
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if (!isfinite(x) || x == 0.0)
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return x;
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hx = __HI(x);
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lx = __LO(x);
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k = (hx & 0x7ff00000) >> 20; /* extract exponent */
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if (k == 0) { /* 0 or subnormal x */
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if ((lx | (hx & 0x7fffffff)) == 0)
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return x; /* +-0 */
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x *= two54;
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hx = __HI(x);
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k = ((hx & 0x7ff00000) >> 20) - 54;
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if (n < -50000)
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return tiny * x; /*underflow*/
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}
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if (k == 0x7ff)
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return x + x; /* NaN or Inf */
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k = k + n;
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if (k > 0x7fe)
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return big * copysign(big, x); /* overflow */
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if (k > 0) /* normal result */
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{
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__HI(x) = (hx & 0x800fffff) | (k << 20);
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return x;
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}
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if (k <= -54)
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if (n > 50000) /* in case integer overflow in n+k */
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return big * copysign(big, x); /*overflow*/
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else
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return tiny * copysign(tiny, x); /*underflow*/
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k += 54; /* subnormal result */
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__HI(x) = (hx & 0x800fffff) | (k << 20);
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return x * twom54;
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} |