Sacado_mpl_is_convertible.hpp

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#ifndef SACADO_MPL_IS_CONVERTIBLE_HPP
#define SACADO_MPL_IS_CONVERTIBLE_HPP

namespace Sacado {

  namespace mpl {

    //
    // A simplified implementation of boost type-trait
    // is_convertible<From,To>.  We use this in a much more limited context
    // within Sacado, and so the easy implementation should always work.
    // We assume From and To are "scalar" types, e.g., are not pointer or
    // reference types.
    //

    struct convertible_impl {
      typedef char yes;       // sizeof(yes) == 1
      typedef char (&no)[2];  // sizeof(no)  == 2

      // A function that takes anything convertible to a To
      template <typename To> static yes tester(To);

      // Overload resolution prefers anything over ...
      template <typename To> static no tester(...);

      // Check if From is convertible to To
      template <typename From, typename To>
      struct checker {
        static From& f;
        static const bool value = sizeof(tester<To>(f)) == sizeof(yes);
      };
    };

    template <typename From, typename To>
    struct is_convertible {
      static const bool value = convertible_impl::checker<From,To>::value;
    };

  }

}

#endif // SACADO_MPL_IS_CONVERTIBLE_HPP