/*
 * EmpiricalPotential.hpp
 *
 *  Created on: Sep 26, 2012
 *      Author: heber
 */

#ifndef EMPIRICALPOTENTIAL_HPP_
#define EMPIRICALPOTENTIAL_HPP_


// include config.h
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <vector>

/** An EmpiricalPotential is a function that is given a vector of objects as
 * arguments which it uses to evaluate an internal function and returns a
 * value representing the energy of this configuration indicated by the
 * arguments.
 *
 * It is to be used inside an std::accumulate function after a vector of
 * arguments (i.e. a vector of a vector) has been prepared initially.
 *
 */
class EmpiricalPotential
{
public:
  /** This class encapsulates all information with respect to a single argument
   *  for a empirical potential function.
   */
  struct argument_t
  {
    //!> indices between which the distance is given
    std::pair<size_t, size_t> indices;
    //!> distance
    double distance;
  };

  //!> typedef on the result value of operator()
  typedef double result_t;
  //!> typedef on the result value of derivative()
  typedef std::vector<result_t> derivative_components_t;
  //!> typedef for the list of argument_t to be given to operator().
  typedef std::vector<argument_t> arguments_t;
public:
  /** Default constructor for class EmpiricalPotential.
   *
   */
  EmpiricalPotential();

  /** Destructor for class EmpiricalPotential.
   *
   */
  virtual ~EmpiricalPotential() {}

  /** This evaluates the internal function with the given list of \a arguments.
   *
   * @param arguments arguments for the internal function
   * @return result of the function evaluation
   */
  result_t operator()(const arguments_t &arguments) const;

  /** This evaluates the first derivative of the internal function with the
   * given list of \a arguments.
   *
   * @param arguments arguments for the internal function
   * @return result vector with same number of components as \a arguments
   */
  derivative_components_t derivative(const arguments_t &arguments) const;
};


#endif /* EMPIRICALPOTENTIAL_HPP_ */