bslalg_selecttrait.h

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/// @file bslalg_selecttrait.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bslalg_selecttrait.h                                               -*-C++-*-
#ifndef INCLUDED_BSLALG_SELECTTRAIT
#define INCLUDED_BSLALG_SELECTTRAIT
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bslalg_selecttrait bslalg_selecttrait
/// @brief  Provide a meta-function to select a suitable trait on a type.
/// @addtogroup bsl
/// @{
/// @addtogroup bslalg
/// @{
/// @addtogroup bslalg_selecttrait
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bslalg_selecttrait-purpose"> Purpose</a>
/// * <a href="#bslalg_selecttrait-classes"> Classes </a>
/// * <a href="#bslalg_selecttrait-description"> Description </a>
///   * <a href="#bslalg_selecttrait-usage"> Usage </a>
///
/// # Purpose {#bslalg_selecttrait-purpose}
/// Provide a meta-function to select a suitable trait on a type.
///
/// @deprecated  Use @ref bslmf_selecttrait  instead.
///
/// # Classes {#bslalg_selecttrait-classes}
///
/// -  bslalg::SelectTrait: trait detection mechanism
///
/// @see 
///
/// # Description {#bslalg_selecttrait-description}
/// This component provides a meta-function, `bslalg::SelectTrait`,
/// for selecting the most appropriate trait from a list of candidate traits for
/// parameterized `TYPE`.
///
/// ## Usage {#bslalg_selecttrait-usage}
///
///
/// @}
/** @} */
/** @} */
 
/** @addtogroup bsl
 * @{
 */
/** @addtogroup bslalg
 * @{
 */
/** @addtogroup bslalg_selecttrait
 * @{
 */
 
#include <bslscm_version.h>
 
#include <bslalg_hastrait.h>
#include <bslalg_typetraitnil.h>
 
#include <bslmf_integralconstant.h>
#include <bslmf_switch.h>
 
 
 
namespace bslalg {
 
                          // =================
                          // class SelectTrait
                          // =================
 
/// Select one trait out of several that the parameterized type `T` may
/// possess.  If `T` has the parameterized trait `TRAIT1`, then the nested
/// `Type` is `TRAIT1`, else if `T` has an optionally parameterized
/// `TRAIT2`, then `Type` is `TRAIT2`, etc.  Also computes an integral
/// selection constant and meta-value.  If `T` has none of the parameterized
/// `TRAIT*`, then the nested `Type` is `TypeTraitNil`.
template <class TYPE,
          class TRAIT1,
          class TRAIT2 = TypeTraitNil,
          class TRAIT3 = TypeTraitNil,
          class TRAIT4 = TypeTraitNil,
          class TRAIT5 = TypeTraitNil>
struct SelectTrait {
 
    // PUBLIC TYPES
    enum {
        /// Integral value indicating which trait was selected: 1 for
        /// `TRAIT1`, 2 for `TRAIT2`, etc., and 0 if none were selected.
        SELECTION = (HasTrait<TYPE, TRAIT1>::value ? 1 :
                     HasTrait<TYPE, TRAIT2>::value ? 2 :
                     HasTrait<TYPE, TRAIT3>::value ? 3 :
                     HasTrait<TYPE, TRAIT4>::value ? 4 :
                     HasTrait<TYPE, TRAIT5>::value ? 5 :
                     0)
    };
 
    /// The actual trait that was selected, or `TypeTraitNil` if no trait
    /// was selected.
    typedef typename bslmf::Switch<SELECTION,
                                   TypeTraitNil,
                                   TRAIT1,
                                   TRAIT2,
                                   TRAIT3,
                                   TRAIT4,
                                   TRAIT5>::Type Type;
};
 
}  // close package namespace
 
#ifndef BDE_OPENSOURCE_PUBLICATION  // BACKWARD_COMPATIBILITY
// ============================================================================
//                           BACKWARD COMPATIBILITY
// ============================================================================
 
#ifdef bslalg_SelectTrait
#undef bslalg_SelectTrait
#endif
/// This alias is defined for backward compatibility.
#define bslalg_SelectTrait bslalg::SelectTrait
#endif  // BDE_OPENSOURCE_PUBLICATION -- BACKWARD_COMPATIBILITY
 
 
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2013 Bloomberg Finance L.P.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// ----------------------------- END-OF-FILE ----------------------------------
 
/** @} */
/** @} */
/** @} */