newlib/libm/complex/ctan.c

   1 /* $NetBSD: ctan.c,v 1.1 2007/08/20 16:01:37 drochner 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  * imported and modified include for newlib 2010/10/03
  32  * Marco Atzeri <marco_atzeri@yahoo.it>
  33  */
  34
  35 /*
  36 FUNCTION
  37         <<ctan>>, <<ctanf>>---complex tangent
  38
  39 INDEX
  40         ctan
  41 INDEX
  42         ctanf
  43
  44 SYNOPSIS
  45        #include <complex.h>
  46        double complex ctan(double complex <[z]>);
  47        float complex ctanf(float complex <[z]>);
  48
  49
  50 DESCRIPTION
  51         These functions compute the complex tangent of <[z]>.
  52
  53         <<ctanf>> is identical to <<ctan>>, except that it performs
  54         its calculations on <<floats complex>>.
  55
  56 RETURNS
  57         These functions return the complex tangent value.
  58
  59 PORTABILITY
  60         <<ctan>> and <<ctanf>> are ISO C99
  61
  62 QUICKREF
  63         <<ctan>> and <<ctanf>> are ISO C99
  64
  65 */
  66
  67
  68 #include <complex.h>
  69 #include <math.h>
  70 #include "cephes_subr.h"
  71
  72 double complex
  73 ctan(double complex z)
  74 {
  75         double complex w;
  76         double d;
  77
  78         d = cos(2.0 * creal(z)) + cosh(2.0 * cimag(z));
  79
  80         if (fabs(d) < 0.25)
  81                 d = _ctans(z);
  82
  83         if (d == 0.0) {
  84                 /* mtherr ("ctan", OVERFLOW); */
  85                 w = HUGE_VAL + HUGE_VAL * I;
  86                 return w;
  87         }
  88
  89         w = sin(2.0 * creal(z)) / d + (sinh(2.0 * cimag(z)) / d) * I;
  90         return w;
  91 }