Program Listing for File nullary_function.hpp

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/*****************************************************************************
** 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_ */