74 lines
1.6 KiB
C
74 lines
1.6 KiB
C
#include <math.h>
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#include <float.h>
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#include <errno.h>
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/*
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This implementation is based largely on Cephes library
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function cabsl (cmplxl.c), which bears the following notice:
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Cephes Math Library Release 2.1: January, 1989
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Copyright 1984, 1987, 1989 by Stephen L. Moshier
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Direct inquiries to 30 Frost Street, Cambridge, MA 02140
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*/
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/*
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Modified for use in libmingwex.a
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02 Sept 2002 Danny Smith <dannysmith@users.sourceforege.net>
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Calls to ldexpl replaced by logbl and calls to frexpl replaced
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by scalbnl to avoid duplicated range checks.
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*/
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extern long double __INFL;
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#define PRECL 32
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long double
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hypotl (long double x, long double y)
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{
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int exx;
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int eyy;
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int scale;
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long double xx =fabsl(x);
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long double yy =fabsl(y);
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if (!isfinite(xx) || !isfinite(yy))
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return xx + yy; /* Return INF or NAN. */
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if (xx == 0.0L)
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return yy;
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if (yy == 0.0L)
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return xx;
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/* Get exponents */
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exx = logbl (xx);
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eyy = logbl (yy);
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/* Check if large differences in scale */
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scale = exx - eyy;
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if ( scale > PRECL)
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return xx;
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if ( scale < -PRECL)
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return yy;
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/* Exponent of approximate geometric mean (x 2) */
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scale = (exx + eyy) >> 1;
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/* Rescale: Geometric mean is now about 2 */
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x = scalbnl(xx, -scale);
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y = scalbnl(yy, -scale);
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xx = sqrtl(x * x + y * y);
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/* Check for overflow and underflow */
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exx = logbl(xx);
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exx += scale;
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if (exx > LDBL_MAX_EXP)
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{
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errno = ERANGE;
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return __INFL;
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}
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if (exx < LDBL_MIN_EXP)
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return 0.0L;
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/* Undo scaling */
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return (scalbnl (xx, scale));
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}
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