unary_compose.hh

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

# include <functional>

#include "utilmm/functional/arg_traits.hh"

namespace utilmm {
  
  template<class UnaryFun1, class UnaryFun2>
  struct unary_compose
    :public std::unary_function<typename UnaryFun2::argument_type,
                                 typename UnaryFun1::result_type> {
  private:
    UnaryFun1 fun_1;
    UnaryFun2 fun_2;    

    typedef typename 
      arg_traits<typename UnaryFun2::argument_type>::type arg_param;

  public:
    unary_compose(UnaryFun1 const &one, UnaryFun2 const &two)
      :fun_1(one), fun_2(two) {}
    
    typename UnaryFun1::result_type operator()(arg_param x)
      const {
      return fun_1(fun_2(x));
    }

  }; // class utilmm::binary_compose_2<>

  template<class Fun1, class Fun2>
  unary_compose<Fun1, Fun2> compose1(Fun1 const &f, Fun2 const &g) {
    return unary_compose<Fun1, Fun2>(f, g);
  }

} // namespace utilmm

#endif // UTILMM_FUNCTIONAL_BINARY_COMPOSE_HEADER