54 lines
1011 B
C
Executable File
54 lines
1011 B
C
Executable File
/* catanl.c */
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/*
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Contributed by Danny Smith
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2005-01-04
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FIXME: This needs some serious numerical analysis.
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*/
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#include <math.h>
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#include <complex.h>
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#include <errno.h>
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/* catan (z) = -I/2 * clog ((I + z) / (I - z)) */
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#ifndef _M_PI_2L
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#define _M_PI_2L 1.5707963267948966192313L
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#endif
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long double complex
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catanl (long double complex Z)
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{
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long double complex Res;
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long double complex Tmp;
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long double x = __real__ Z;
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long double y = __imag__ Z;
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if ( x == 0.0L && (1.0L - fabsl (y)) == 0.0L)
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{
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errno = ERANGE;
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__real__ Res = HUGE_VALL;
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__imag__ Res = HUGE_VALL;
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}
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else if (isinf (hypotl (x, y)))
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{
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__real__ Res = (x > 0 ? _M_PI_2L : -_M_PI_2L);
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__imag__ Res = 0.0L;
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}
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else
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{
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__real__ Tmp = - x;
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__imag__ Tmp = 1.0L - y;
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__real__ Res = x;
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__imag__ Res = y + 1.0L;
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Tmp = clogl (Res/Tmp);
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__real__ Res = - 0.5L * __imag__ Tmp;
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__imag__ Res = 0.5L * __real__ Tmp;
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}
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return Res;
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}
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