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Diffstat (limited to 'src/complex/catanl.c')
| -rw-r--r-- | src/complex/catanl.c | 126 |
1 files changed, 126 insertions, 0 deletions
diff --git a/src/complex/catanl.c b/src/complex/catanl.c new file mode 100644 index 00000000..5ace7704 --- /dev/null +++ b/src/complex/catanl.c @@ -0,0 +1,126 @@ +/* origin: OpenBSD /usr/src/lib/libm/src/s_catanl.c */ +/* + * Copyright (c) 2008 Stephen L. Moshier <steve@moshier.net> + * + * Permission to use, copy, modify, and distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR + * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN + * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF + * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + */ +/* + * Complex circular arc tangent + * + * + * SYNOPSIS: + * + * long double complex catanl(); + * long double complex z, w; + * + * w = catanl( z ); + * + * + * DESCRIPTION: + * + * If + * z = x + iy, + * + * then + * 1 ( 2x ) + * Re w = - arctan(-----------) + k PI + * 2 ( 2 2) + * (1 - x - y ) + * + * ( 2 2) + * 1 (x + (y+1) ) + * Im w = - log(------------) + * 4 ( 2 2) + * (x + (y-1) ) + * + * Where k is an arbitrary integer. + * + * + * ACCURACY: + * + * Relative error: + * arithmetic domain # trials peak rms + * DEC -10,+10 5900 1.3e-16 7.8e-18 + * IEEE -10,+10 30000 2.3e-15 8.5e-17 + * The check catan( ctan(z) ) = z, with |x| and |y| < PI/2, + * had peak relative error 1.5e-16, rms relative error + * 2.9e-17. See also clog(). + */ + +#include <complex.h> +#include <float.h> +#include "libm.h" + +#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024 +long double complex catanl(long double complex z) +{ + return catan(z); +} +#else +static const long double PIL = 3.141592653589793238462643383279502884197169L; +static const long double DP1 = 3.14159265358979323829596852490908531763125L; +static const long double DP2 = 1.6667485837041756656403424829301998703007e-19L; +static const long double DP3 = 1.8830410776607851167459095484560349402753e-39L; + +static long double redupil(long double x) +{ + long double t; + long i; + + t = x / PIL; + if (t >= 0.0L) + t += 0.5L; + else + t -= 0.5L; + + i = t; /* the multiple */ + t = i; + t = ((x - t * DP1) - t * DP2) - t * DP3; + return t; +} + +long double complex catanl(long double complex z) +{ + long double complex w; + long double a, t, x, x2, y; + + x = creall(z); + y = cimagl(z); + + if ((x == 0.0L) && (y > 1.0L)) + goto ovrf; + + x2 = x * x; + a = 1.0L - x2 - (y * y); + if (a == 0.0L) + goto ovrf; + + t = atan2l(2.0L * x, a) * 0.5L; + w = redupil(t); + + t = y - 1.0L; + a = x2 + (t * t); + if (a == 0.0L) + goto ovrf; + + t = y + 1.0L; + a = (x2 + (t * t)) / a; + w = w + (0.25L * logl(a)) * I; + return w; + +ovrf: + // FIXME + w = LDBL_MAX + LDBL_MAX * I; + return w; +} +#endif |