1: /* Return arc hyperbole cosine for double 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: 
   25: __complex__ double
   26: __cacosh (__complex__ double x)
   27: {
   28:   __complex__ double res;
   29:   int rcls = fpclassify (__real__ x);
   30:   int icls = fpclassify (__imag__ x);
   31: 
   32:   if (rcls <= FP_INFINITE || icls <= FP_INFINITE)
   33:     {
   34:       if (icls == FP_INFINITE)
   35:         {
   36:           __real__ res = HUGE_VAL;
   37: 
   38:           if (rcls == FP_NAN)
   39:             __imag__ res = __nan ("");
   40:           else
   41:             __imag__ res = __copysign ((rcls == FP_INFINITE
   42:                                         ? (__real__ x < 0.0
   43:                                            ? M_PI - M_PI_4 : M_PI_4)
   44:                                         : M_PI_2), __imag__ x);
   45:         }
   46:       else if (rcls == FP_INFINITE)
   47:         {
   48:           __real__ res = HUGE_VAL;
   49: 
   50:           if (icls >= FP_ZERO)
   51:             __imag__ res = __copysign (signbit (__real__ x) ? M_PI : 0.0,
   52:                                        __imag__ x);
   53:           else
   54:             __imag__ res = __nan ("");
   55:         }
   56:       else
   57:         {
   58:           __real__ res = __nan ("");
   59:           __imag__ res = __nan ("");
   60:         }
   61:     }
   62:   else if (rcls == FP_ZERO && icls == FP_ZERO)
   63:     {
   64:       __real__ res = 0.0;
   65:       __imag__ res = __copysign (M_PI_2, __imag__ x);
   66:     }
   67:   else
   68:     {
   69:       __complex__ double y;
   70: 
   71:       __real__ y = (__real__ x - __imag__ x) * (__real__ x + __imag__ x) - 1.0;
   72:       __imag__ y = 2.0 * __real__ x * __imag__ x;
   73: 
   74:       y = __csqrt (y);
   75: 
   76:       if (__real__ x < 0.0)
   77:         y = -y;
   78: 
   79:       __real__ y += __real__ x;
   80:       __imag__ y += __imag__ x;
   81: 
   82:       res = __clog (y);
   83: 
   84:       /* We have to use the positive branch.  */
   85:       if (__real__ res < 0.0)
   86:         res = -res;
   87:     }
   88: 
   89:   return res;
   90: }
   91: weak_alias (__cacosh, cacosh)
   92: #ifdef NO_LONG_DOUBLE
   93: strong_alias (__cacosh, __cacoshl)
   94: weak_alias (__cacosh, cacoshl)
   95: #endif