source: lemon-0.x/src/work/marci/lp/expression.h @ 1097:c91e765266d7

// -*- c++ -*-
#ifndef LEMON_EXPRESSION_H
#define LEMON_EXPRESSION_H

#include <iostream>
#include <map>

namespace lemon {

  /*! \brief Linear expression

    \c Expr<_Col,_Value> implements a class of linear expressions with the 
    operations of addition and multiplication with scalar. 

    \author Marton Makai
   */
  template <typename _Col, typename _Value>
  class Expr;

  template <typename _Col, typename _Value>
  class Expr {
  protected:
    typedef 
    typename std::map<_Col, _Value> Data; 
    Data data;
  public:
    Expr() { }
    Expr(_Col _col) { 
      data.insert(std::make_pair(_col, 1));
    }
    Expr& operator*=(_Value _value) {
      for (typename Data::iterator i=data.begin(); 
           i!=data.end(); ++i) {
        (*i).second *= _value;
      }
      return *this;
    }
    Expr& operator+=(const Expr<_Col, _Value>& expr) {
      for (typename Data::const_iterator j=expr.data.begin(); 
           j!=expr.data.end(); ++j) {
        typename Data::iterator i=data.find((*j).first);
        if (i==data.end()) {
          data.insert(std::make_pair((*j).first, (*j).second));
        } else {
          (*i).second+=(*j).second;
        }
      }
      return *this;
    }
    template <typename _C, typename _V> 
    friend std::ostream& operator<<(std::ostream& os, 
                                    const Expr<_C, _V>& expr);
  };

  template <typename _Col, typename _Value>
  Expr<_Col, _Value> operator*(_Value _value, _Col _col) {
    Expr<_Col, _Value> tmp(_col);
    tmp*=_value;
    return tmp;
  }

  template <typename _Col, typename _Value>
  Expr<_Col, _Value> operator*(_Value _value, 
                               const Expr<_Col, _Value>& expr) {
    Expr<_Col, _Value> tmp(expr);
    tmp*=_value;
    return tmp;
  }

  template <typename _Col, typename _Value>
  Expr<_Col, _Value> operator+(const Expr<_Col, _Value>& expr1, 
                               const Expr<_Col, _Value>& expr2) {
    Expr<_Col, _Value> tmp(expr1);
    tmp+=expr2;
    return tmp;
  }

  template <typename _Col, typename _Value>
  std::ostream& operator<<(std::ostream& os, 
                           const Expr<_Col, _Value>& expr) {
    for (typename Expr<_Col, _Value>::Data::const_iterator i=
           expr.data.begin(); 
         i!=expr.data.end(); ++i) {
      os << (*i).second << "*" << (*i).first << " ";
    }
    return os;
  }
  
} //namespace lemon

#endif //LEMON_EXPRESSION_H