#ifndef OPERATOR_HPP
#define OPERATOR_HPP

template<typename T>
T infinity() { }
template<>
float infinity() {
  return INFINITY;
}

#include <vector>

template<typename T>
struct VariableAssignment;
template<typename T>
struct Expression;

template<typename T>
struct Operator {
  virtual T operator() (const std::vector< Expression<T>* >&, const VariableAssignment<T>&) const = 0;
};
template<typename T>
struct Maximum : public Operator<T> {
  virtual T operator() (const std::vector< Expression<T>* >& args, const VariableAssignment<T>& assignment) const {
    T value = -infinity<T>();
    for (typename std::vector< Expression<T>* >::const_iterator it = args.begin();
         it != args.end();
         ++it) {
      T temporary = (**it)(assignment);
      value = (temporary < value ? value : temporary);
    }
    return value;
  }
};
template<typename T>
struct Minimum : public Operator<T> {
  virtual T operator() (const std::vector< Expression<T>* >& args, const VariableAssignment<T>& assignment) const {
    T value = infinity<T>();
    for (typename std::vector< Expression<T>* >::const_iterator it = args.begin();
         it != args.end();
         ++it) {
      T temporary = (**it)(assignment);
      value = (temporary > value ? value : temporary);
    }
    return value;
  }
};

template<typename T>
struct Constant : public Operator<T> {
  Constant(const T& val)
    : _value(val) { }
  T operator() (const std::vector< Expression<T>* >& args, const VariableAssignment<T>& ass) const {
    return _value;
  }
  private:
  const T _value;
};

template<typename T>
struct Addition: public Operator<T> {
  T operator() (const std::vector< Expression<T>* >& args, const VariableAssignment<T>& ass) const {
    T sum = (*args[0])(ass);
    for (unsigned int i = 1, size = args.size(); i < size; ++i) {
      sum += (*args[i])(ass);
    }
    return sum;
  }
};

template<typename T>
struct Subtraction: public Operator<T> {
  T operator() (const std::vector< Expression<T>* >& args, const VariableAssignment<T>& ass) const {
    T sum = (*args[0])(ass);
    for (unsigned int i = 1, size = args.size(); i < size; ++i) {
      sum -= (*args[i])(ass);
    }
    return sum;
  }
};

#include "VariableAssignment.hpp"
#include "Expression.hpp"

#endif