utils.hh

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/* -*- C++ -*-
 * $Id: utils.hh 957 2005-03-07 16:01:20Z sjoyeux $
 */
#ifndef UTILMM_FUNCTIONAL_UTILS_HEADER
# define UTILMM_FUNCTIONAL_UTILS_HEADER

#include "utilmm/functional/arg_traits.hh"
# include <functional>

namespace utilmm {

  template<typename Ty>
  struct identity :public std::unary_function<Ty, Ty> {
  private:
    typedef typename arg_traits<Ty>::type arg_type;
    
  public:
    arg_type operator()(arg_type x) const {
      return x;
    }
  }; // struct utilmm::identity<>

  template<class Pair>
  struct select_1st
    :public std::unary_function<Pair, typename Pair::first_type> {
    typename Pair::first_type const &operator()(Pair const &p) const {
      return p.first;
    }
  }; // struct utilmm::select_1st<>

  template<class Pair>
  struct select_2nd
    :public std::unary_function<Pair, typename Pair::second_type> {
    typename Pair::second_type const &operator()(Pair const &p) const {
      return p.second;
    }
  }; // struct utilmm::select_2nd<>

} // namespace utilmm

#endif // UTILMM_FUNCTIONAL_UTILS_HEADER