bslmf_addconst.h

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/// @file bslmf_addconst.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bslmf_addconst.h                                                   -*-C++-*-
#ifndef INCLUDED_BSLMF_ADDCONST
#define INCLUDED_BSLMF_ADDCONST
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bslmf_addconst bslmf_addconst
/// @brief  Provide a meta-function for adding a top-level `const`-qualifier.
/// @addtogroup bsl
/// @{
/// @addtogroup bslmf
/// @{
/// @addtogroup bslmf_addconst
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bslmf_addconst-purpose"> Purpose</a>
/// * <a href="#bslmf_addconst-classes"> Classes </a>
/// * <a href="#bslmf_addconst-description"> Description </a>
///   * <a href="#bslmf_addconst-usage"> Usage </a>
///     * <a href="#bslmf_addconst-example-1-adding-a-const-qualifier-to-a-type"> Example 1: Adding a const-qualifier to a Type </a>
///
/// # Purpose {#bslmf_addconst-purpose}
/// Provide a meta-function for adding a top-level `const`-qualifier.
///
/// # Classes {#bslmf_addconst-classes}
///
/// -  bsl::add_const: meta-function for adding a top-level `const`-qualifier
/// -  bsl::add_const_t: alias to the return type of the meta-function
///
/// @see  bslmf_removeconst
///
/// # Description {#bslmf_addconst-description}
/// This component defines a meta-function, `bsl::add_const` and
/// declares an `bsl::add_const_t` alias to the return type of the
/// `bsl::add_const`, that may be used to add a top-level `const`-qualifier to a
/// type if it is not a reference type, nor a function type, nor already
/// `const`-qualified at the top-level.
///
/// `bsl::add_const` and `bsl::add_const_t` meet the requirements of the
/// @ref add_const  template defined in the C++11 standard [meta.trans.cv].
///
/// ## Usage {#bslmf_addconst-usage}
///
///
/// In this section we show intended use of this component.
///
/// ### Example 1: Adding a const-qualifier to a Type {#bslmf_addconst-example-1-adding-a-const-qualifier-to-a-type}
///
///
/// Suppose that we want to add a `const`-qualifier to a particular type.
///
/// First, we create two `typedef`s -- a `const`-qualified type (`MyConstType`)
/// and the same type without the `const`-qualifier (`MyType`):
/// @code
/// typedef int       MyType;
/// typedef const int MyConstType;
/// @endcode
/// Now, we add a `const`-qualifier to `MyType` using `bsl::add_const` and
/// verify that the resulting type is the same as `MyConstType`:
/// @code
/// assert(true ==
///          (bsl::is_same<bsl::add_const<MyType>::type, MyConstType>::value));
/// @endcode
/// Finally, if the current compiler supports alias templates C++11 feature, we
/// add a `const`-qualifier to `MyType` using `bsl::add_const_t` and verify that
/// the resulting type is the same as `MyConstType`:
/// @code
/// #ifdef BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES
///   assert(true ==
///                (bsl::is_same<bsl::add_const_t<MyType>, MyConstType>::value));
/// #endif
/// @endcode
/// Note, that the `bsl::add_const_t` avoids the `::type` suffix and `typename`
/// prefix when we want to use the result of the `bsl::add_const` meta-function
/// in templates.
/// @}
/** @} */
/** @} */
 
/** @addtogroup bsl
 * @{
 */
/** @addtogroup bslmf
 * @{
 */
/** @addtogroup bslmf_addconst
 * @{
 */
 
#include <bslscm_version.h>
 
#include <bslmf_isconst.h>
#include <bslmf_isfunction.h>
#include <bslmf_isreference.h>
 
#include <bsls_compilerfeatures.h>
 
 
namespace bslmf {
 
                         // ===================
                         // struct AddConst_Imp
                         // ===================
 
/// This `struct` template provides an alias `Type` that adds a
/// `const`-qualifier to the (template parameter) `t_TYPE` if the (template
/// parameter) `t_ADD_CONST_FLAG` is `true`.  This generic default template
/// adds the `const`-qualifier to `t_TYPE` in the `Type` alias.  A template
/// specialization (below) leaves `t_TYPE` as-is in its `Type` alias.
template <class t_TYPE, bool t_ADD_CONST_FLAG>
struct AddConst_Imp {
 
    // PUBLIC TYPES
 
    /// This `typedef` is an alias to a type that is the same as the
    /// (template parameter) `t_TYPE` except that a top-level
    /// `const`-qualifier has been added.
    typedef t_TYPE const Type;
};
 
                     // ==================================
                     // struct AddConst_Imp<t_TYPE, false>
                     // ==================================
 
/// This partial specialization of `AddConst_Imp`, for when the (template
/// parameter) `t_ADD_CONST_FLAG` is `false`, provides an alias `Type` that
/// has the same type as the (template parameter) `t_TYPE`.
template <class t_TYPE>
struct AddConst_Imp<t_TYPE, false> {
 
    // PUBLIC TYPES
 
    /// This `typedef` is an alias to the (template parameter) `t_TYPE`.
    typedef t_TYPE Type;
};
 
}  // close package namespace
 
 
namespace bsl {
 
                         // ================
                         // struct add_const
                         // ================
 
/// This `struct` template implements the @ref add_const  meta-function defined
/// in the C++11 standard [meta.trans.cv], providing an alias, `type`, that
/// returns the result.  If the (template parameter) `t_TYPE` is not a
/// reference type, nor a function type, nor already `const`-qualified at
/// the top-level, then `type` is an alias to `t_TYPE` with a top-level
/// `const`-qualifier added; otherwise, `type` is an alias to `t_TYPE`.
template <class t_TYPE>
struct add_const {
 
    // PUBLIC TYPES
 
    /// This `typedef` is an alias to the (template parameter) `t_TYPE` with
    /// a top-level `const`-qualifier added if `t_TYPE` is not a reference,
    /// nor a function, nor already `const`-qualified; otherwise, `type` is
    /// an alias to `t_TYPE`.
    typedef typename BloombergLP::bslmf::AddConst_Imp<
        t_TYPE,
        !is_reference<t_TYPE>::value && !is_function<t_TYPE>::value &&
            !is_const<t_TYPE>::value>::Type type;
};
 
#ifdef BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES
 
// ALIASES
 
/// `add_const_t` is an alias to the return type of the @ref add_const 
/// meta-function.  Note, that the `add_const_t` avoids the `::type` suffix
/// and `typename` prefix when we want to use the result of the
/// meta-function in templates.
template <class t_TYPE>
using add_const_t = typename add_const<t_TYPE>::type;
#endif  // BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES
 
}  // close namespace bsl
 
#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 ----------------------------------
 
/** @} */
/** @} */
/** @} */