text: /* Support routines for the intrinsic power (**) operator.
     Copyright 2004, 2007, 2009 Free Software Foundation, Inc.
     Contributed by Paul Brook
  
  This file is part of the GNU Fortran 95 runtime library (libgfortran).
  
  Libgfortran is free software; you can redistribute it and/or
  modify it under the terms of the GNU General Public
  License as published by the Free Software Foundation; either
  version 3 of the License, or (at your option) any later version.
  
  Libgfortran is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.
  
  Under Section 7 of GPL version 3, you are granted additional
  permissions described in the GCC Runtime Library Exception, version
  3.1, as published by the Free Software Foundation.
  
  You should have received a copy of the GNU General Public License and
  a copy of the GCC Runtime Library Exception along with this program;
  see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  <http://www.gnu.org/licenses/>.  */
  
  #include "libgfortran.h"
  
  
  /* Use Binary Method to calculate the powi. This is not an optimal but
     a simple and reasonable arithmetic. See section 4.6.3, "Evaluation of
     Powers" of Donald E. Knuth, "Seminumerical Algorithms", Vol. 2, "The Art
     of Computer Programming", 3rd Edition, 1998.  */
  
  #if defined (HAVE_GFC_COMPLEX_16) && defined (HAVE_GFC_INTEGER_16)
  
  GFC_COMPLEX_16 pow_c16_i16 (GFC_COMPLEX_16 a, GFC_INTEGER_16 b);
  export_proto(pow_c16_i16);
  
  GFC_COMPLEX_16
  pow_c16_i16 (GFC_COMPLEX_16 a, GFC_INTEGER_16 b)
  {
    GFC_COMPLEX_16 pow, x;
    GFC_INTEGER_16 n;
    GFC_UINTEGER_16 u;
    
    n = b;
    x = a;
    pow = 1;
    if (n != 0)
      {
        if (n < 0)
  	{
  
  	  u = -n;
  	  x = pow / x;
  	}
        else
  	{
  	   u = n;
  	}
        for (;;)
  	{
  	  if (u & 1)
  	    pow *= x;
  	  u >>= 1;
  	  if (u)
  	    x *= x;
  	  else
  	    break;
  	}
      }
    return pow;
  }
  
  #endif
  