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      1 /* $NetBSD: catan.c,v 1.2 2011/07/03 06:45:24 mrg Exp $ */
      2 
      3 /*-
      4  * Copyright (c) 2007 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software written by Stephen L. Moshier.
      8  * It is redistributed by the NetBSD Foundation by permission of the author.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 #include "../src/namespace.h"
     33 #include <complex.h>
     34 #include <math.h>
     35 #include <float.h>
     36 #include "cephes_subr.h"
     37 
     38 #ifdef __weak_alias
     39 __weak_alias(catan, _catan)
     40 #endif
     41 
     42 #define MAXNUM DBL_MAX
     43 
     44 double complex
     45 catan(double complex z)
     46 {
     47 	double complex w;
     48 	double a, t, x, x2, y;
     49 
     50 	x = creal(z);
     51 	y = cimag(z);
     52 
     53 	if ((x == 0.0) && (y > 1.0))
     54 		goto ovrf;
     55 
     56 	x2 = x * x;
     57 	a = 1.0 - x2 - (y * y);
     58 	if (a == 0.0)
     59 		goto ovrf;
     60 
     61 	t = 0.5 * atan2(2.0 * x, a);
     62 	w = _redupi(t);
     63 
     64 	t = y - 1.0;
     65 	a = x2 + (t * t);
     66 	if (a == 0.0)
     67 		goto ovrf;
     68 
     69 	t = y + 1.0;
     70 	a = (x2 + (t * t))/a;
     71 	w = w + (0.25 * log(a)) * I;
     72 	return w;
     73 
     74 ovrf:
     75 #if 0
     76 	mtherr ("catan", OVERFLOW);
     77 #endif
     78 	w = MAXNUM + MAXNUM * I;
     79 	return w;
     80 }
     81