bslmf_isaccessiblebaseof.h

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/// @file bslmf_isaccessiblebaseof.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bslmf_isaccessiblebaseof.h                                         -*-C++-*-
#ifndef INCLUDED_BSLMF_ISACCESSIBLEBASEOF
#define INCLUDED_BSLMF_ISACCESSIBLEBASEOF
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bslmf_isaccessiblebaseof bslmf_isaccessiblebaseof
/// @brief  Provide a compile-time check for derived classes.
/// @addtogroup bsl
/// @{
/// @addtogroup bslmf
/// @{
/// @addtogroup bslmf_isaccessiblebaseof
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bslmf_isaccessiblebaseof-purpose"> Purpose</a>
/// * <a href="#bslmf_isaccessiblebaseof-classes"> Classes </a>
/// * <a href="#bslmf_isaccessiblebaseof-description"> Description </a>
///   * <a href="#bslmf_isaccessiblebaseof-usage"> Usage </a>
///     * <a href="#bslmf_isaccessiblebaseof-example-1-base-and-derived-classes"> Example 1: Base And Derived Classes </a>
///     * <a href="#bslmf_isaccessiblebaseof-example-2-unrelated-classes"> Example 2: Unrelated Classes </a>
///
/// # Purpose {#bslmf_isaccessiblebaseof-purpose}
/// Provide a compile-time check for derived classes.
///
/// # Classes {#bslmf_isaccessiblebaseof-classes}
///
/// -  bslmf::IsAccessibleBaseOf: meta-function for detecting derived classes
///
/// # Description {#bslmf_isaccessiblebaseof-description}
/// This component provides a meta-function,
/// `bslmf::IsAccessibleBaseOf`, that determines whether one class is an
/// accessible base class of another class.  The static constant
/// `bslmf::IsAccessibleBaseOf::value` is `true` if the template parameter
/// `t_BASE` class is an accessible base class of, or the same class as, the
/// template parameter `t_DERIVED`.  Otherwise,
/// `bslmf::IsAccessibleBaseOf::value` is `false`.  The specific cases of
/// private, protected, and ambiguous inheritance are not supported for versions
/// of C++ prior to 11.
///
/// ## Usage {#bslmf_isaccessiblebaseof-usage}
///
///
/// In this section we show intended use of this component.
///
/// ### Example 1: Base And Derived Classes {#bslmf_isaccessiblebaseof-example-1-base-and-derived-classes}
///
///
/// Define two classes, one inheriting from the other.
/// @code
/// struct Base
/// {};
///
/// struct Derived : Base
/// {};
/// @endcode
/// Evaluate `bslmf::IsAccessibleBaseOf::value`.
/// @code
/// void example1()
/// {
///     assert((true  == bslmf::IsAccessibleBaseOf<Base,    Derived>::value));
///     assert((true  == bslmf::IsAccessibleBaseOf<Base,    Base>   ::value));
///     assert((true  == bslmf::IsAccessibleBaseOf<Derived, Derived>::value));
///     assert((false == bslmf::IsAccessibleBaseOf<Derived, Base>   ::value));
/// }
/// @endcode
/// ### Example 2: Unrelated Classes {#bslmf_isaccessiblebaseof-example-2-unrelated-classes}
///
///
/// Define two classes, one inheriting privately from the other.
/// @code
/// class Unrelated
/// {};
///
/// class Unrelated2
/// {};
/// @endcode
/// Evaluate `bslmf::IsAccessibleBaseOf::value`.  Note that `Derived` is not
/// *observably* derived from `Base`, so std::is_base_of would evaluate `true`,
/// but `bslmf::IsAccessibleBaseOf` evaluates `false`.
/// @code
/// void example2()
/// {
///     assert((false ==
///             bslmf::IsAccessibleBaseOf<Unrelated, Unrelated2>::value));
/// }
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bsl
 * @{
 */
/** @addtogroup bslmf
 * @{
 */
/** @addtogroup bslmf_isaccessiblebaseof
 * @{
 */
 
#include <bslscm_version.h>
 
#include <bslmf_integralconstant.h>
#include <bslmf_isclass.h>
#include <bslmf_isconvertible.h>
#include <bslmf_removecv.h>
 
 
namespace bslmf {
 
                          // ========================
                          // class IsAccessibleBaseOf
                          // ========================
 
/// This `struct` template provides a type trait to determine if one class
/// is an accessible base class of another class.  Note that, while similar
/// to `std::is_base_of`, when the derived relationship is via private,
/// protected, or ambiguous inheritance `IsAccessibleBaseOf` evaluates to
/// false.
template <class t_BASE, class t_DERIVED>
class IsAccessibleBaseOf
: public bsl::integral_constant<
      bool,
      bsl::is_class<typename bsl::remove_cv<t_BASE>::type>::value &&
          bsl::is_class<typename bsl::remove_cv<t_DERIVED>::type>::value &&
          bsl::is_convertible<
              typename bsl::remove_cv<t_DERIVED>::type *,
              typename bsl::remove_cv<t_BASE>::type *>::value> {
};
 
}  // close package namespace
 
 
#endif  // INCLUDED_BSLMF_ISACCESSIBLEBASEOF
 
// ----------------------------------------------------------------------------
// Copyright 2022 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 ----------------------------------
 
/** @} */
/** @} */
/** @} */