ext/OGDF/src/basic/Math.cpp

   1 /*
   2  * $Revision: 2549 $
   3  *
   4  * last checkin:
   5  *   $Author: gutwenger $
   6  *   $Date: 2012-07-04 23:09:19 +0200 (Mi, 04. Jul 2012) $
   7  ***************************************************************/
   8
   9 /** \file
  10  * \brief Implementation of mathematical constants, functions.
  11  *
  12  * \author Carsten Gutwenger
  13  *
  14  * \par License:
  15  * This file is part of the Open Graph Drawing Framework (OGDF).
  16  *
  17  * \par
  18  * Copyright (C)<br>
  19  * See README.txt in the root directory of the OGDF installation for details.
  20  *
  21  * \par
  22  * This program is free software; you can redistribute it and/or
  23  * modify it under the terms of the GNU General Public License
  24  * Version 2 or 3 as published by the Free Software Foundation;
  25  * see the file LICENSE.txt included in the packaging of this file
  26  * for details.
  27  *
  28  * \par
  29  * This program is distributed in the hope that it will be useful,
  30  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  31  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  32  * GNU General Public License for more details.
  33  *
  34  * \par
  35  * You should have received a copy of the GNU General Public
  36  * License along with this program; if not, write to the Free
  37  * Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  38  * Boston, MA 02110-1301, USA.
  39  *
  40  * \see  http://www.gnu.org/copyleft/gpl.html
  41  ***************************************************************/
  42
  43
  44 #include <ogdf/basic/Math.h>
  45 #include <limits.h>
  46
  47
  48 namespace ogdf {
  49
  50
  51         const double Math::pi     = 3.14159265358979323846;
  52         const double Math::pi_2   = 1.57079632679489661923;
  53         const double Math::pi_4   = 0.785398163397448309616;
  54         const double Math::two_pi = 2*3.14159265358979323846;
  55
  56         const double Math::e    = 2.71828182845904523536;
  57
  58         const double Math::log_of_2 = log(2.0);
  59         const double Math::log_of_4 = log(4.0);
  60
  61         int factorials[13] = {
  62                 1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880,
  63                 3628800, 39916800, 479001600
  64         };
  65
  66         double factorials_d[20] = {
  67                 1.0, 1.0, 2.0, 6.0, 24.0, 120.0, 720.0, 5040.0, 40320.0, 362880.0,
  68                 3628800.0, 39916800.0, 479001600.0, 6227020800.0, 87178291200.0,
  69                 1307674368000.0, 20922789888000.0, 355687428096000.0,
  70                 6402373705728000.0, 121645100408832000.0
  71         };
  72
  73         int Math::binomial(int n, int k)
  74         {
  75                 if(k>n/2) k = n-k;
  76                 if(k == 0) return 1;
  77                 int r = n;
  78                 for(int i = 2; i<=k; ++i)
  79                         r = (r * (n+1-i))/i;
  80                 return r;
  81         }
  82
  83         double Math::binomial_d(int n, int k)
  84         {
  85                 if(k>n/2) k = n-k;
  86                 if(k == 0) return 1.0;
  87                 double r = n;
  88                 for(int i = 2; i<=k; ++i)
  89                         r = (r * (n+1-i))/i;
  90                 return r;
  91         }
  92
  93         int Math::factorial(int n)
  94         {
  95                 if(n < 0) return 1;
  96                 if(n > 12) return INT_MAX; // not representable by int
  97
  98                 return factorials[n];
  99         }
 100
 101         double Math::factorial_d(int n)
 102         {
 103                 if(n < 0) return 1.0;
 104
 105                 double f = 1.0;
 106                 for(; n > 19; --n)
 107                         f *= n;
 108
 109                 return f * factorials_d[n];
 110         }
 111
 112 } // namespace ogdf