Sacado_mpl_has_type.hpp

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//                           Sacado Package
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#ifndef SACADO_MPL_HAS_TYPE_HPP
#define SACADO_MPL_HAS_TYPE_HPP

namespace Sacado {

  namespace mpl {

    // Uses SFINAE to determine if a type has a nested typedef called "type",
    // i.e., whether the type is a metafunction

    typedef char NotFound;           // sizeof(NotFound) == 1
    struct Found { char x[2]; };     // sizeof(Found) == 2

    // Overload matches if and only if T::type exists
    template <class T> Found testHasType(typename T::type*);

    // Compiler prefers anything at all over ...
    template <class T> NotFound testHasType(...);

    template <class T> struct has_type {
      static const bool value = (sizeof(testHasType<T>(0)) == sizeof(Found));
    };

  } // namespace mpl

} // namespace Sacado

#endif // SACADO_MPL_HAS_TYPE_HPP