include/dai/var.h

   1 /*  Copyright (C) 2006-2008  Joris Mooij  [joris dot mooij at tuebingen dot mpg dot de]
   2     Radboud University Nijmegen, The Netherlands /
   3     Max Planck Institute for Biological Cybernetics, Germany
   4
   5     Copyright (C) 2002  Martijn Leisink  [martijn@mbfys.kun.nl]
   6     Radboud University Nijmegen, The Netherlands
   7
   8     This file is part of libDAI.
   9
  10     libDAI is free software; you can redistribute it and/or modify
  11     it under the terms of the GNU General Public License as published by
  12     the Free Software Foundation; either version 2 of the License, or
  13     (at your option) any later version.
  14
  15     libDAI is distributed in the hope that it will be useful,
  16     but WITHOUT ANY WARRANTY; without even the implied warranty of
  17     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18     GNU General Public License for more details.
  19
  20     You should have received a copy of the GNU General Public License
  21     along with libDAI; if not, write to the Free Software
  22     Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  23 */
  24
  25
  26 /// \file
  27 /// \brief Defines class Var
  28
  29
  30 #ifndef __defined_libdai_var_h
  31 #define __defined_libdai_var_h
  32
  33
  34 #include <iostream>
  35
  36
  37 namespace dai {
  38
  39
  40 /// Represents a discrete random variable.
  41 /** A Var stores the \a label of the variable (an integer-valued unique ID)
  42  *  and the number of possible values (\a states) of that variable. Two
  43  *  Var objects with the same label are assumed to be identical (i.e., it
  44  *  is assumed that their states are also the same).
  45  *
  46  *  In this manual, we use the following notational conventions. The discrete
  47  *  random variable with label \f$l\f$ is denoted as \f$x_l\f$, and the number
  48  *  of possible values of this variable as \f$S_l\f$; this is represented in
  49  *  code by the object Var(\f$l\f$,\f$S_l\f$). The set of possible values of
  50  *  variable \f$x_l\f$ is denoted \f$X_l := \{0,1,\dots,S_l-1\}\f$.
  51  */
  52 class Var {
  53     private:
  54         /// Label of the variable (its unique ID)
  55         long    _label;
  56
  57         /// Number of possible values
  58         size_t  _states;
  59
  60     public:
  61         /// Default constructor
  62         Var() : _label(-1), _states(0) {}
  63         /// Constructor
  64         Var( long label, size_t states ) : _label(label), _states(states) {}
  65
  66         /// Returns the label
  67         long label() const { return _label; }
  68         /// Returns reference to label
  69         long & label() { return _label; }
  70
  71         /// Returns the number of states
  72         size_t states () const { return _states; }
  73         /// Returns reference to number of states
  74         size_t& states () { return _states; }
  75
  76         /// Smaller-than operator (compares only labels)
  77         bool operator < ( const Var& n ) const { return( _label <  n._label ); }
  78         /// Larger-than operator (compares only labels)
  79         bool operator > ( const Var& n ) const { return( _label >  n._label ); }
  80         /// Smaller-than-or-equal-to operator (compares only labels)
  81         bool operator <= ( const Var& n ) const { return( _label <= n._label ); }
  82         /// Larger-than-or-equal-to operator (compares only labels)
  83         bool operator >= ( const Var& n ) const { return( _label >= n._label ); }
  84         /// Not-equal-to operator (compares only labels)
  85         bool operator != ( const Var& n ) const { return( _label != n._label ); }
  86         /// Equal-to operator (compares only labels)
  87         bool operator == ( const Var& n ) const { return( _label == n._label ); }
  88
  89         /// Writes a Var to an output stream
  90         friend std::ostream& operator << ( std::ostream& os, const Var& n ) {
  91             return( os << "x" << n.label() );
  92         }
  93 };
  94
  95
  96 } // end of namespace dai
  97
  98
  99 #endif