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Diffstat (limited to 'ACE/ace/If_Then_Else.h')
-rw-r--r-- | ACE/ace/If_Then_Else.h | 89 |
1 files changed, 89 insertions, 0 deletions
diff --git a/ACE/ace/If_Then_Else.h b/ACE/ace/If_Then_Else.h new file mode 100644 index 00000000000..163219e206b --- /dev/null +++ b/ACE/ace/If_Then_Else.h @@ -0,0 +1,89 @@ +// -*- C++ -*- + +//============================================================================= +/** + * @file If_Then_Else.h + * + * @c ACE::If_Then_Else traits template based on the @c IfThenElse + * template described in the book "C++ Templates" by Vandevoorde and + * Josuttis. + * + * $Id$ + * + * @author Ossama Othman <ossama@dre.vanderbilt.edu> + */ +//============================================================================= + +#ifndef ACE_IF_THEN_ELSE_H +#define ACE_IF_THEN_ELSE_H + +#include "ace/config-lite.h" + +ACE_BEGIN_VERSIONED_NAMESPACE_DECL + +namespace ACE +{ + + /** + * @struct If_Then_Else + * + * @brief Compile-time selection of type based on a boolean value. + * + * This primary template selects the second or third argument based + * on the value of the boolean first argument. + * + * Usage example: + * + * \code + * + * template <typename T> + * class Foo + * { + * public: + * // Set "TheType" to be the larger of "T" and "int". + * typedef typename If_Then_Else<(sizeof (T) > sizeof (int)), + * T, + * int>::result_type TheType; + * }; + * + * \endcode + * + * @note This merely a forward declaration since we really only care + * about the partial specializations below. + */ + template <bool C, typename Ta, typename Tb> + struct If_Then_Else; + + /** + * @struct If_Then_Else + * + * @brief Select of type @a Ta if boolean value is @c true. + * + * This partial specialization selects the type @a Ta if the boolean + * first argument is @c true. + */ + template <typename Ta, typename Tb> + struct If_Then_Else<true, Ta, Tb> + { + typedef Ta result_type; + }; + + /** + * @struct If_Then_Else + * + * @brief Select of type @a Tb if boolean value is @c false. + * + * This partial specialization selects the type @a Tb if the boolean + * first argument is @c false. + */ + template <typename Ta, typename Tb> + struct If_Then_Else<false, Ta, Tb> + { + typedef Tb result_type; + }; + +} + +ACE_END_VERSIONED_NAMESPACE_DECL + +#endif /* ACE_IF_THEN_ELSE_H */ |