include/dai/var.h

   1 /*  This file is part of libDAI - http://www.libdai.org/
   2  *
   3  *  libDAI is licensed under the terms of the GNU General Public License version
   4  *  2, or (at your option) any later version. libDAI is distributed without any
   5  *  warranty. See the file COPYING for more details.
   6  *
   7  *  Copyright (C) 2002       Martijn Leisink  [martijn@mbfys.kun.nl]
   8  *  Copyright (C) 2006-2009  Joris Mooij      [joris dot mooij at libdai dot org]
   9  *  Copyright (C) 2002-2007  Radboud University Nijmegen, The Netherlands
  10  */
  11
  12
  13 /// \file
  14 /// \brief Defines class Var
  15
  16
  17 #ifndef __defined_libdai_var_h
  18 #define __defined_libdai_var_h
  19
  20
  21 #include <iostream>
  22 #include <cassert>
  23
  24
  25 namespace dai {
  26
  27
  28 /// Represents a discrete random variable.
  29 /** A Var stores the \a label of the variable (an integer-valued unique ID)
  30  *  and the number of possible values (\a states) of that variable. Two
  31  *  Var objects with the same label are assumed to be identical (i.e., it
  32  *  is assumed that their states are also the same).
  33  *
  34  *  In this manual, we use the following notational conventions. The discrete
  35  *  random variable with label \f$l\f$ is denoted as \f$x_l\f$, and the number
  36  *  of possible values of this variable as \f$S_l\f$; this is represented in
  37  *  code by the object Var(\f$l\f$,\f$S_l\f$). The set of possible values of
  38  *  variable \f$x_l\f$ is denoted \f$X_l := \{0,1,\dots,S_l-1\}\f$.
  39  */
  40 class Var {
  41     private:
  42         /// Label of the variable (its unique ID)
  43         long    _label;
  44
  45         /// Number of possible values
  46         size_t  _states;
  47
  48     public:
  49         /// Default constructor
  50         Var() : _label(-1), _states(0) {}
  51         /// Constructor
  52         Var( long label, size_t states ) : _label(label), _states(states) {}
  53
  54         /// Returns the label
  55         long label() const { return _label; }
  56         /// Returns reference to label
  57         long & label() { return _label; }
  58
  59         /// Returns the number of states
  60         size_t states () const { return _states; }
  61         /// Returns reference to number of states
  62         size_t& states () { return _states; }
  63
  64         /// Smaller-than operator (compares only labels)
  65         bool operator < ( const Var& n ) const { return( _label <  n._label ); }
  66         /// Larger-than operator (compares only labels)
  67         bool operator > ( const Var& n ) const { return( _label >  n._label ); }
  68         /// Smaller-than-or-equal-to operator (only compares labels)
  69         bool operator <= ( const Var& n ) const {
  70 #ifdef DAI_DEBUG
  71             if( _label == n._label )
  72                 assert( _states == n._states );
  73 #endif
  74             return( _label <= n._label );
  75         }
  76         /// Larger-than-or-equal-to operator (only compares labels)
  77         bool operator >= ( const Var& n ) const {
  78 #ifdef DAI_DEBUG
  79             if( _label == n._label )
  80                 assert( _states == n._states );
  81 #endif
  82             return( _label >= n._label );
  83         }
  84         /// Not-equal-to operator (only compares labels)
  85         bool operator != ( const Var& n ) const {
  86 #ifdef DAI_DEBUG
  87             if( _label == n._label )
  88                 assert( _states == n._states );
  89 #endif
  90             return( _label != n._label );
  91         }
  92         /// Equal-to operator (only compares labels)
  93         bool operator == ( const Var& n ) const {
  94 #ifdef DAI_DEBUG
  95             if( _label == n._label )
  96                 assert( _states == n._states );
  97 #endif
  98             return( _label == n._label );
  99         }
 100
 101         /// Writes a Var to an output stream
 102         friend std::ostream& operator << ( std::ostream& os, const Var& n ) {
 103             return( os << "x" << n.label() );
 104         }
 105 };
 106
 107
 108 } // end of namespace dai
 109
 110
 111 #endif