.. _program_listing_file__tmp_ws_src_ecl_core_ecl_concepts_include_ecl_concepts_nullary_function.hpp:

Program Listing for File nullary_function.hpp
=============================================

|exhale_lsh| :ref:`Return to documentation for file <file__tmp_ws_src_ecl_core_ecl_concepts_include_ecl_concepts_nullary_function.hpp>` (``/tmp/ws/src/ecl_core/ecl_concepts/include/ecl/concepts/nullary_function.hpp``)

.. |exhale_lsh| unicode:: U+021B0 .. UPWARDS ARROW WITH TIP LEFTWARDS

.. code-block:: cpp

   
   /*****************************************************************************
   ** Ifdefs
   *****************************************************************************/
   
   #ifndef ECL_CONCEPTS_NULLARY_FUNCTION_HPP_
   #define ECL_CONCEPTS_NULLARY_FUNCTION_HPP_
   
   /*****************************************************************************
   ** Includes
   *****************************************************************************/
   
   #include <ecl/config/macros.hpp>
   
   #include "macros.hpp"
   
   /*****************************************************************************
   ** Namespaces
   *****************************************************************************/
   
   namespace ecl {
   
   /*****************************************************************************
   ** Concept [Container]
   *****************************************************************************/
   
   template <typename Implementation>
   class NullaryFunctionConcept {
       public:
   
           ecl_compile_time_concept_test(NullaryFunctionConcept)
           {
                   typedef typename Implementation::result_type ECL_UNUSED return_type;
               function();
               // Unfortunately we can't test for the result type to match a certain value here
               // as this would then have 2 template arguments with a separating comma. That throws
               // the compile_time_concept_check macro into thinking it has two macro arguments.
           }
   
       private:
           // Putting instantiations here actually saves instantiation (which can cause a
           // problem if there is no default constructor).
           Implementation function;
   };
   
   } // namespace ecl
   
   #endif /* ECL_CONCEPTS_NULLARY_FUNCTION_HPP_ */