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// -*- 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 */
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