bslmf_removecvref.h

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/// @file bslmf_removecvref.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bslmf_removecvref.h                                                -*-C++-*-
#ifndef INCLUDED_BSLMF_REMOVECVREF
#define INCLUDED_BSLMF_REMOVECVREF
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bslmf_removecvref bslmf_removecvref
/// @brief  Provide a meta-func for removing reference-ness and cv-qualifiers.
/// @addtogroup bsl
/// @{
/// @addtogroup bslmf
/// @{
/// @addtogroup bslmf_removecvref
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bslmf_removecvref-purpose"> Purpose</a>
/// * <a href="#bslmf_removecvref-classes"> Classes </a>
/// * <a href="#bslmf_removecvref-description"> Description </a>
///   * <a href="#bslmf_removecvref-usage"> Usage </a>
///     * <a href="#bslmf_removecvref-example-1-removing-the-cv-qualifiers-and-reference-ness-of-a-type"> Example 1: Removing the CV-Qualifiers and Reference-ness of a Type </a>
///
/// # Purpose {#bslmf_removecvref-purpose}
/// Provide a meta-func for removing reference-ness and cv-qualifiers.
///
/// # Classes {#bslmf_removecvref-classes}
///
/// -  bsl::remove_cvref: meta-func for removing reference-ness and cv-qualifiers
/// -  bsl::remove_cvref_t: alias to the return type of the meta-function
///
/// @see  bslmf_removecv, bslmf_removereference
///
/// # Description {#bslmf_removecvref-description}
/// This component defines a meta-function, `bsl::remove_cvref`,
/// and declares a `bsl::remove_cvref_t` alias to the return type of the
/// `bsl::remove_cvref`, that may be used to strip reference-ness (including
/// both lvalue and rvalue reference-ness, if the latter is supported by the
/// compiler) and to remove any top-level cv-qualifiers (`const`-qualifier and
/// `volatile`-qualifier) from a type.
///
/// `bsl::remove_cvref` and  `bsl::remove_cvref_t` meet the requirements of the
/// @ref remove_cvref  template defined in the C++20 standard [meta.trans.other].
///
/// ## Usage {#bslmf_removecvref-usage}
///
///
/// In this section we show intended use of this component.
///
/// ### Example 1: Removing the CV-Qualifiers and Reference-ness of a Type {#bslmf_removecvref-example-1-removing-the-cv-qualifiers-and-reference-ness-of-a-type}
///
///
/// Suppose that we want to remove the cv-qualifiers from a particular type.
///
/// First, we create two `typedef`s -- a `const`-qualified and
/// `volatile`-qualified reference type (`MyCvRefType`) and the same type
/// without the cv-qualifiers and reference-ness (`MyType`):
/// @code
///     typedef const volatile int& MyCvRefType;
///     typedef                int  MyType;
/// @endcode
/// Now, we remove the cv-qualifiers from `MyCvRefType` and its reference-ness
/// using `bsl::remove_cvref` and verify that the resulting type is the same as
/// `MyType`:
/// @code
///     assert(true == (bsl::is_same<bsl::remove_cvref<MyCvRefType>::type,
///                                  MyType>::value));
/// @endcode
/// Finally, if the current compiler supports alias templates C++11 feature, we
/// remove a `const`-qualifier, `volatile`-qualifier and its reference-ness from
/// `MyCvRefType` using `bsl::remove_cvref_t` and verify that the resulting type
/// is the same as `MyType`:
/// @code
/// #ifdef BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES
///       assert(
///           true ==
///           (bsl::is_same<bsl::remove_cvref_t<MyCvRefType>, MyType>::value));
/// #endif
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bsl
 * @{
 */
/** @addtogroup bslmf
 * @{
 */
/** @addtogroup bslmf_removecvref
 * @{
 */
 
#include <bslscm_version.h>
 
#include <bslmf_removecv.h>
#include <bslmf_removereference.h>
 
#include <bsls_compilerfeatures.h>
#include <bsls_libraryfeatures.h>
 
#ifdef BSLS_LIBRARYFEATURES_HAS_CPP20_BASELINE_LIBRARY
#include <type_traits> // 'std::remove_cvref', 'std::remove_cvref_t'
#endif
 
namespace bsl {
 
#ifdef BSLS_LIBRARYFEATURES_HAS_CPP20_BASELINE_LIBRARY
using std::remove_cvref;
#else
 
                         // ===================
                         // struct remove_cvref
                         // ===================
 
/// This `struct` template implements the @ref remove_cvref  meta-function
/// defined in the C++20 standard [meta.trans.other], providing an alias,
/// `type`, that returns the result.  `type` has the same type as the
/// (template parameter) `t_TYPE` except that its reference-ness has been
/// stripped and any top-level cv-qualifiers have been removed.
///
/// See @ref bslmf_removecvref 
template <class t_TYPE>
struct remove_cvref {
 
    // PUBLIC TYPES
 
    /// This `typedef` is an alias to the same type as the (template
    /// parameter) `t_TYPE` except that its reference-ness has been stripped
    /// and any top-level cv-qualifier has been removed.
    typedef typename bsl::remove_cv<
        typename bsl::remove_reference<t_TYPE>::type>::type type;
};
#endif // BSLS_LIBRARYFEATURES_HAS_CPP20_BASELINE_LIBRARY
 
#ifdef BSLS_LIBRARYFEATURES_HAS_CPP20_BASELINE_LIBRARY
using std::remove_cvref_t;
 
#else
#ifdef BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES
// ALIASES
template <class t_TYPE>
using remove_cvref_t = typename remove_cvref<t_TYPE>::type;
    // @ref remove_cvref_t  is an alias to the return type of the
    // 'bsl::remove_cvref' meta-function.  Note, that the @ref remove_cvref_t 
    // avoids the '::type' suffix and 'typename' prefix when we want to use the
    // result of the meta-function in templates.
 
#endif // BSLS_LIBRARYFEATURES_HAS_CPP20_BASELINE_LIBRARY
 
#endif  // BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES
 
}  // close namespace bsl
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2021 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 ----------------------------------
 
/** @} */
/** @} */
/** @} */