1: /* Return arc hyperbole cosine for float value.
    2:    Copyright (C) 1997, 2006 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 Lesser General Public
    8:    License as published by the Free Software Foundation; either
    9:    version 2.1 of the 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:    Lesser General Public License for more details.
   15: 
   16:    You should have received a copy of the GNU Lesser General Public
   17:    License along with the GNU C Library; if not, write to the Free
   18:    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   19:    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:       if (__real__ x < 0.0)
   79:         y = -y;
   80: 
   81:       __real__ y += __real__ x;
   82:       __imag__ y += __imag__ x;
   83: 
   84:       res = __clogf (y);
   85: #else
   86:       float re2 = __real__ x * __real__ x;
   87:       float im2 = __imag__ x * __imag__ x;
   88:       float sq = re2 - im2 - 1.0;
   89:       float ro = __ieee754_sqrtf (sq * sq + 4 * re2 * im2);
   90:       float a = __ieee754_sqrtf ((sq + ro) / 2.0);
   91:       float b = __ieee754_sqrtf ((-sq + ro) / 2.0);
   92: 
   93:       __real__ res = 0.5 * __ieee754_logf (re2 + __real__ x * 2 * a
   94:                                            + im2 + __imag__ x * 2 * b
   95:                                            + ro);
   96:       __imag__ res = __ieee754_atan2f (__imag__ x + b, __real__ x + a);
   97: #endif
   98: 
   99:       /* We have to use the positive branch.  */
  100:       if (__real__ res < 0.0)
  101:         res = -res;
  102:     }
  103: 
  104:   return res;
  105: }
  106: #ifndef __cacoshf
  107: weak_alias (__cacoshf, cacoshf)
  108: #endif