bslstl_monostate.h

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/// @file bslstl_monostate.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bslstl_monostate.h                                                 -*-C++-*-
#ifndef INCLUDED_BSLSTL_MONOSTATE
#define INCLUDED_BSLSTL_MONOSTATE
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bslstl_monostate bslstl_monostate
/// @brief  Provide a default constructible alternative for `bsl::variant`.
/// @addtogroup bsl
/// @{
/// @addtogroup bslstl
/// @{
/// @addtogroup bslstl_monostate
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bslstl_monostate-purpose"> Purpose</a>
/// * <a href="#bslstl_monostate-classes"> Classes </a>
/// * <a href="#bslstl_monostate-description"> Description </a>
///
/// # Purpose {#bslstl_monostate-purpose}
/// Provide a default constructible alternative for `bsl::variant`.
///
/// # Classes {#bslstl_monostate-classes}
///
/// -  bsl::monostate: default constructible `bsl::variant` first alternative
///
/// @see  bslstl_variant
///
/// # Description {#bslstl_monostate-description}
/// This component provides a `bsl::monostate` class.  This class
/// can serve as a first alternative type for a `bsl::variant` to make the
/// `bsl::variant` type default constructible.
/// @}
/** @} */
/** @} */
 
/** @addtogroup bsl
 * @{
 */
/** @addtogroup bslstl
 * @{
 */
/** @addtogroup bslstl_monostate
 * @{
 */
 
 
#include <bslscm_version.h>
 
#include <bsls_compilerfeatures.h>
#include <bsls_keyword.h>
#include <bsls_libraryfeatures.h>
 
#ifdef BSLS_LIBRARYFEATURES_HAS_CPP17_BASELINE_LIBRARY
#include <variant>  // for 'std::monostate'
#include <bslh_hashvariant.h>
#endif  // BSLS_LIBRARYFEATURES_HAS_CPP17_BASELINE_LIBRARY
 
#ifdef BSLS_LIBRARYFEATURES_HAS_CPP17_BASELINE_LIBRARY
namespace bsl {
using std::monostate;
}  // close namespace bsl
#else
namespace bsl {
                              // ===============
                              // struct monostate
                              // ===============
 
struct monostate {
 
};
 
// FREE OPERATORS
 
/// Compare two `monostate` objects.  Since `monostate` only has one value,
/// the result is `true` for the `==`, `<=`, and `>=` operators, and `false`
/// for the `!=`, `<`, and `>` operators.
BSLS_KEYWORD_CONSTEXPR bool operator==(monostate,
                                       monostate) BSLS_KEYWORD_NOEXCEPT;
BSLS_KEYWORD_CONSTEXPR bool operator!=(monostate,
                                       monostate) BSLS_KEYWORD_NOEXCEPT;
BSLS_KEYWORD_CONSTEXPR bool operator<(monostate,
                                      monostate) BSLS_KEYWORD_NOEXCEPT;
BSLS_KEYWORD_CONSTEXPR bool operator>(monostate,
                                      monostate) BSLS_KEYWORD_NOEXCEPT;
BSLS_KEYWORD_CONSTEXPR bool operator<=(monostate,
                                       monostate) BSLS_KEYWORD_NOEXCEPT;
BSLS_KEYWORD_CONSTEXPR bool operator>=(monostate,
                                       monostate) BSLS_KEYWORD_NOEXCEPT;
 
/// Pass a `monostate` to the specified `hashAlg`, where `hashAlg` is a
/// hashing algorithm.
template <class t_HASHALG>
void hashAppend(t_HASHALG& hashAlg, const monostate&);
}  // close namespace bsl
#endif  // BSLS_LIBRARYFEATURES_HAS_CPP17_BASELINE_LIBRARY
 
// ============================================================================
//                           INLINE DEFINITIONS
// ============================================================================
#ifndef BSLS_LIBRARYFEATURES_HAS_CPP17_BASELINE_LIBRARY
namespace bsl {
 
inline BSLS_KEYWORD_CONSTEXPR
bool operator==(monostate, monostate) BSLS_KEYWORD_NOEXCEPT
{
    return true;
}
 
inline BSLS_KEYWORD_CONSTEXPR
bool operator!=(monostate, monostate) BSLS_KEYWORD_NOEXCEPT
{
    return false;
}
 
inline BSLS_KEYWORD_CONSTEXPR
bool operator<(monostate, monostate) BSLS_KEYWORD_NOEXCEPT
{
    return false;
}
 
inline BSLS_KEYWORD_CONSTEXPR
bool operator>(monostate, monostate) BSLS_KEYWORD_NOEXCEPT
{
    return false;
}
 
inline BSLS_KEYWORD_CONSTEXPR
bool operator<=(monostate, monostate) BSLS_KEYWORD_NOEXCEPT
{
    return true;
}
 
inline BSLS_KEYWORD_CONSTEXPR
bool operator>=(monostate, monostate) BSLS_KEYWORD_NOEXCEPT
{
    return true;
}
 
template <class t_HASHALG>
void hashAppend(t_HASHALG& hashAlg, const monostate&)
{
    hashAppend(hashAlg, -7777);
}
}  // close namespace bsl
#endif  // BSLS_LIBRARYFEATURES_HAS_CPP17_BASELINE_LIBRARY
#endif  // INCLUDED_BSLSTL_MONOSTATE
 
// ----------------------------------------------------------------------------
// Copyright 2023 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 ----------------------------------
 
/** @} */
/** @} */
/** @} */