xapian-core/common/log2.h

   1 /** @file log2.h
   2  * @brief Defines a log2() function to find the logarithm to base 2 if not already defined in the library.
   3  */
   4 /* Copyright (C) 2013 Aarsh Shah
   5  * Copyright (C) 2014,2015 Olly Betts
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
  20  */
  21
  22 #ifndef XAPIAN_INCLUDED_LOG2_H
  23 #define XAPIAN_INCLUDED_LOG2_H
  24
  25 #ifndef PACKAGE
  26 # error config.h must be included first in each C++ source file
  27 #endif
  28
  29 #include <cmath>
  30 #if !HAVE_DECL_LOG2
  31 inline double log2(double x) { return std::log(x) / std::log(2.0); }
  32 #endif
  33
  34 #endif // XAPIAN_INCLUDED_LOG2_H