lib/libm/complex/catan.c

   1 /* $NetBSD$ */
   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 "cephes_subr.h"
  36
  37 #ifdef __weak_alias
  38 __weak_alias(catan, _catan)
  39 #endif
  40
  41 #define MAXNUM 1.0e308
  42
  43 double complex
  44 catan(double complex z)
  45 {
  46         double complex w;
  47         double a, t, x, x2, y;
  48
  49         x = creal(z);
  50         y = cimag(z);
  51
  52         if ((x == 0.0) && (y > 1.0))
  53                 goto ovrf;
  54
  55         x2 = x * x;
  56         a = 1.0 - x2 - (y * y);
  57         if (a == 0.0)
  58                 goto ovrf;
  59
  60         t = 0.5 * atan2(2.0 * x, a);
  61         w = _redupi(t);
  62
  63         t = y - 1.0;
  64         a = x2 + (t * t);
  65         if (a == 0.0)
  66                 goto ovrf;
  67
  68         t = y + 1.0;
  69         a = (x2 + (t * t))/a;
  70         w = w + (0.25 * log(a)) * I;
  71         return w;
  72
  73 ovrf:
  74 #if 0
  75         mtherr ("catan", OVERFLOW);
  76 #endif
  77         w = MAXNUM + MAXNUM * I;
  78         return w;
  79 }