sysdeps/libm-ieee754/s_cacoshf.c

   1 /* Return arc hyperbole cosine for float value.
   2    Copyright (C) 1997 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Library General Public License as
   8    published by the Free Software Foundation; either version 2 of the
   9    License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Library General Public License for more details.
  15
  16    You should have received a copy of the GNU Library General Public
  17    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  18    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 #include <complex.h>
  22 #include <math.h>
  23
  24 #include "math_private.h"
  25
  26 __complex__ float
  27 __cacoshf (__complex__ float x)
  28 {
  29   __complex__ float res;
  30   int rcls = fpclassify (__real__ x);
  31   int icls = fpclassify (__imag__ x);
  32
  33   if (rcls <= FP_INFINITE || icls <= FP_INFINITE)
  34     {
  35       if (icls == FP_INFINITE)
  36         {
  37           __real__ res = HUGE_VALF;
  38
  39           if (rcls == FP_NAN)
  40             __imag__ res = __nanf ("");
  41           else
  42             __imag__ res = __copysignf ((rcls == FP_INFINITE
  43                                          ? (__real__ x < 0.0
  44                                             ? M_PI - M_PI_4 : M_PI_4)
  45                                          : M_PI_2), __imag__ x);
  46         }
  47       else if (rcls == FP_INFINITE)
  48         {
  49           __real__ res = HUGE_VALF;
  50
  51           if (icls >= FP_ZERO)
  52             __imag__ res = __copysignf (signbit (__real__ x) ? M_PI : 0.0,
  53                                         __imag__ x);
  54           else
  55             __imag__ res = __nanf ("");
  56         }
  57       else
  58         {
  59           __real__ res = __nanf ("");
  60           __imag__ res = __nanf ("");
  61         }
  62     }
  63   else if (rcls == FP_ZERO && icls == FP_ZERO)
  64     {
  65       __real__ res = 0.0;
  66       __imag__ res = __copysignf (M_PI_2, __imag__ x);
  67     }
  68   else
  69     {
  70 #if 1
  71       __complex__ float y;
  72
  73       __real__ y = (__real__ x - __imag__ x) * (__real__ x + __imag__ x) - 1.0;
  74       __imag__ y = 2.0 * __real__ x * __imag__ x;
  75
  76       y = __csqrtf (y);
  77
  78       __real__ y += __real__ x;
  79       __imag__ y += __imag__ x;
  80
  81       res = __clogf (y);
  82 #else
  83       float re2 = __real__ x * __real__ x;
  84       float im2 = __imag__ x * __imag__ x;
  85       float sq = re2 - im2 - 1.0;
  86       float ro = __ieee754_sqrtf (sq * sq + 4 * re2 * im2);
  87       float a = __ieee754_sqrtf ((sq + ro) / 2.0);
  88       float b = __ieee754_sqrtf ((-sq + ro) / 2.0);
  89
  90       __real__ res = 0.5 * __ieee754_logf (re2 + __real__ x * 2 * a
  91                                            + im2 + __imag__ x * 2 * b
  92                                            + ro);
  93       __imag__ res = __ieee754_atan2f (__imag__ x + b, __real__ x + a);
  94 #endif
  95     }
  96
  97   return res;
  98 }
  99 weak_alias (__cacoshf, cacoshf)