librheolef-dev 6.5-1+b1 / usr / include / rheolef / gamma.icc

/// This file is part of Rheolef.
///
/// Copyright (C) 2000-2009 Pierre Saramito 
///
/// Rheolef 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 2 of the License, or
/// (at your option) any later version.
///
/// Rheolef 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.
///
/// You should have received a copy of the GNU General Public License
/// along with Rheolef; if not, write to the Free Software
/// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
/// lexer for qmg mesh files
/// =========================================================================
#include <cmath>
#include <cstdlib>
template <class T> T my_gamma (const T& x) {
	if (x == T(0)) return 1;
	if (x == T(int(x))) {
    	    T value = 1;
    	    for (size_t n = int(x)-1; n > 0; n--)
      	        value *= T(n);
	    // warning_macro ("gamma(" << x << ") = " << value);
    	    return value;
	}
  	static T sqrt_pi = sqrt(acos(T(-1.)));
  	if (x == -T(0.5)) return -2*sqrt_pi;
  	if (x-int(x) == T(0.5)) { 
	    T value = sqrt_pi;
	    for (size_t n = int(x); n != 0; n--)
	       value *= (n-0.5);
    	    return value;
  	}
  	std::cerr << "gamma: " << x << " is not of integer of half order" << std::endl;
  	exit (1);
  	return 0;
}