//
// Copyright (c) 2014-2021 Martin Moene
//
// https://github.com/martinmoene/optional-lite
//
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#pragma once
#ifndef NONSTD_OPTIONAL_LITE_HPP
#define NONSTD_OPTIONAL_LITE_HPP
#define optional_lite_MAJOR 3
#define optional_lite_MINOR 6
#define optional_lite_PATCH 0
#define optional_lite_VERSION optional_STRINGIFY(optional_lite_MAJOR) "." optional_STRINGIFY(optional_lite_MINOR) "." optional_STRINGIFY(optional_lite_PATCH)
#define optional_STRINGIFY( x ) optional_STRINGIFY_( x )
#define optional_STRINGIFY_( x ) #x
// optional-lite configuration:
#define optional_OPTIONAL_DEFAULT 0
#define optional_OPTIONAL_NONSTD 1
#define optional_OPTIONAL_STD 2
// tweak header support:
#ifdef __has_include
# if __has_include()
# include
# endif
#define optional_HAVE_TWEAK_HEADER 1
#else
#define optional_HAVE_TWEAK_HEADER 0
//# pragma message("optional.hpp: Note: Tweak header not supported.")
#endif
// optional selection and configuration:
#if !defined( optional_CONFIG_SELECT_OPTIONAL )
# define optional_CONFIG_SELECT_OPTIONAL ( optional_HAVE_STD_OPTIONAL ? optional_OPTIONAL_STD : optional_OPTIONAL_NONSTD )
#endif
// Control presence of extensions:
#ifndef optional_CONFIG_NO_EXTENSIONS
#define optional_CONFIG_NO_EXTENSIONS 0
#endif
// Control marking class bad_optional_access and several methods with [[nodiscard]]]:
#if !defined(optional_CONFIG_NO_NODISCARD)
# define optional_CONFIG_NO_NODISCARD 0
#else
# define optional_CONFIG_NO_NODISCARD 1
#endif
// Control presence of exception handling (try and auto discover):
#ifndef optional_CONFIG_NO_EXCEPTIONS
# if defined(_MSC_VER)
# include // for _HAS_EXCEPTIONS
# endif
# if defined(__cpp_exceptions) || defined(__EXCEPTIONS) || (defined(_HAS_EXCEPTIONS) && (_HAS_EXCEPTIONS))
# define optional_CONFIG_NO_EXCEPTIONS 0
# else
# define optional_CONFIG_NO_EXCEPTIONS 1
# endif
#endif
// C++ language version detection (C++23 is speculative):
// Note: VC14.0/1900 (VS2015) lacks too much from C++14.
#ifndef optional_CPLUSPLUS
# if defined(_MSVC_LANG ) && !defined(__clang__)
# define optional_CPLUSPLUS (_MSC_VER == 1900 ? 201103L : _MSVC_LANG )
# else
# define optional_CPLUSPLUS __cplusplus
# endif
#endif
#define optional_CPP98_OR_GREATER ( optional_CPLUSPLUS >= 199711L )
#define optional_CPP11_OR_GREATER ( optional_CPLUSPLUS >= 201103L )
#define optional_CPP11_OR_GREATER_ ( optional_CPLUSPLUS >= 201103L )
#define optional_CPP14_OR_GREATER ( optional_CPLUSPLUS >= 201402L )
#define optional_CPP17_OR_GREATER ( optional_CPLUSPLUS >= 201703L )
#define optional_CPP20_OR_GREATER ( optional_CPLUSPLUS >= 202002L )
#define optional_CPP23_OR_GREATER ( optional_CPLUSPLUS >= 202300L )
// C++ language version (represent 98 as 3):
#define optional_CPLUSPLUS_V ( optional_CPLUSPLUS / 100 - (optional_CPLUSPLUS > 200000 ? 2000 : 1994) )
// Use C++17 std::optional if available and requested:
#if optional_CPP17_OR_GREATER && defined(__has_include )
# if __has_include( )
# define optional_HAVE_STD_OPTIONAL 1
# else
# define optional_HAVE_STD_OPTIONAL 0
# endif
#else
# define optional_HAVE_STD_OPTIONAL 0
#endif
#define optional_USES_STD_OPTIONAL ( (optional_CONFIG_SELECT_OPTIONAL == optional_OPTIONAL_STD) || ((optional_CONFIG_SELECT_OPTIONAL == optional_OPTIONAL_DEFAULT) && optional_HAVE_STD_OPTIONAL) )
//
// in_place: code duplicated in any-lite, expected-lite, optional-lite, value-ptr-lite, variant-lite:
//
#ifndef nonstd_lite_HAVE_IN_PLACE_TYPES
#define nonstd_lite_HAVE_IN_PLACE_TYPES 1
// C++17 std::in_place in :
#if optional_CPP17_OR_GREATER
#include
namespace nonstd {
using std::in_place;
using std::in_place_type;
using std::in_place_index;
using std::in_place_t;
using std::in_place_type_t;
using std::in_place_index_t;
#define nonstd_lite_in_place_t( T) std::in_place_t
#define nonstd_lite_in_place_type_t( T) std::in_place_type_t
#define nonstd_lite_in_place_index_t(K) std::in_place_index_t
#define nonstd_lite_in_place( T) std::in_place_t{}
#define nonstd_lite_in_place_type( T) std::in_place_type_t{}
#define nonstd_lite_in_place_index(K) std::in_place_index_t{}
} // namespace nonstd
#else // optional_CPP17_OR_GREATER
#include
namespace nonstd {
namespace detail {
template< class T >
struct in_place_type_tag {};
template< std::size_t K >
struct in_place_index_tag {};
} // namespace detail
struct in_place_t {};
template< class T >
inline in_place_t in_place( detail::in_place_type_tag /*unused*/ = detail::in_place_type_tag() )
{
return in_place_t();
}
template< std::size_t K >
inline in_place_t in_place( detail::in_place_index_tag /*unused*/ = detail::in_place_index_tag() )
{
return in_place_t();
}
template< class T >
inline in_place_t in_place_type( detail::in_place_type_tag /*unused*/ = detail::in_place_type_tag() )
{
return in_place_t();
}
template< std::size_t K >
inline in_place_t in_place_index( detail::in_place_index_tag /*unused*/ = detail::in_place_index_tag() )
{
return in_place_t();
}
// mimic templated typedef:
#define nonstd_lite_in_place_t( T) nonstd::in_place_t(&)( nonstd::detail::in_place_type_tag )
#define nonstd_lite_in_place_type_t( T) nonstd::in_place_t(&)( nonstd::detail::in_place_type_tag )
#define nonstd_lite_in_place_index_t(K) nonstd::in_place_t(&)( nonstd::detail::in_place_index_tag )
#define nonstd_lite_in_place( T) nonstd::in_place_type
#define nonstd_lite_in_place_type( T) nonstd::in_place_type
#define nonstd_lite_in_place_index(K) nonstd::in_place_index
} // namespace nonstd
#endif // optional_CPP17_OR_GREATER
#endif // nonstd_lite_HAVE_IN_PLACE_TYPES
//
// Using std::optional:
//
#if optional_USES_STD_OPTIONAL
#include
namespace nonstd {
using std::optional;
using std::bad_optional_access;
using std::hash;
using std::nullopt;
using std::nullopt_t;
using std::operator==;
using std::operator!=;
using std::operator=;
using std::make_optional;
using std::swap;
}
#else // optional_USES_STD_OPTIONAL
#include
#include
// optional-lite alignment configuration:
#ifndef optional_CONFIG_MAX_ALIGN_HACK
# define optional_CONFIG_MAX_ALIGN_HACK 0
#endif
#ifndef optional_CONFIG_ALIGN_AS
// no default, used in #if defined()
#endif
#ifndef optional_CONFIG_ALIGN_AS_FALLBACK
# define optional_CONFIG_ALIGN_AS_FALLBACK double
#endif
// Compiler warning suppression:
#if defined(__clang__)
# pragma clang diagnostic push
# pragma clang diagnostic ignored "-Wundef"
#elif defined(__GNUC__)
# pragma GCC diagnostic push
# pragma GCC diagnostic ignored "-Wundef"
#elif defined(_MSC_VER )
# pragma warning( push )
#endif
// half-open range [lo..hi):
#define optional_BETWEEN( v, lo, hi ) ( (lo) = 1910 optional_COMPILER_MSVC_VERSION == 141 (Visual Studio 2017)
// MSVC++ 14.2 _MSC_VER >= 1920 optional_COMPILER_MSVC_VERSION == 142 (Visual Studio 2019)
#if defined(_MSC_VER ) && !defined(__clang__)
# define optional_COMPILER_MSVC_VER (_MSC_VER )
# define optional_COMPILER_MSVC_VERSION (_MSC_VER / 10 - 10 * ( 5 + (_MSC_VER < 1900 ) ) )
#else
# define optional_COMPILER_MSVC_VER 0
# define optional_COMPILER_MSVC_VERSION 0
#endif
#define optional_COMPILER_VERSION( major, minor, patch ) ( 10 * (10 * (major) + (minor) ) + (patch) )
#if defined(__GNUC__) && !defined(__clang__)
# define optional_COMPILER_GNUC_VERSION optional_COMPILER_VERSION(__GNUC__, __GNUC_MINOR__, __GNUC_PATCHLEVEL__)
#else
# define optional_COMPILER_GNUC_VERSION 0
#endif
#if defined(__clang__)
# define optional_COMPILER_CLANG_VERSION optional_COMPILER_VERSION(__clang_major__, __clang_minor__, __clang_patchlevel__)
#else
# define optional_COMPILER_CLANG_VERSION 0
#endif
#if optional_BETWEEN(optional_COMPILER_MSVC_VERSION, 70, 140 )
# pragma warning( disable: 4345 ) // initialization behavior changed
#endif
#if optional_BETWEEN(optional_COMPILER_MSVC_VERSION, 70, 150 )
# pragma warning( disable: 4814 ) // in C++14 'constexpr' will not imply 'const'
#endif
// Presence of language and library features:
#define optional_HAVE(FEATURE) ( optional_HAVE_##FEATURE )
#ifdef _HAS_CPP0X
# define optional_HAS_CPP0X _HAS_CPP0X
#else
# define optional_HAS_CPP0X 0
#endif
// Unless defined otherwise below, consider VC14 as C++11 for optional-lite:
#if optional_COMPILER_MSVC_VER >= 1900
# undef optional_CPP11_OR_GREATER
# define optional_CPP11_OR_GREATER 1
#endif
#define optional_CPP11_90 (optional_CPP11_OR_GREATER_ || optional_COMPILER_MSVC_VER >= 1500)
#define optional_CPP11_100 (optional_CPP11_OR_GREATER_ || optional_COMPILER_MSVC_VER >= 1600)
#define optional_CPP11_110 (optional_CPP11_OR_GREATER_ || optional_COMPILER_MSVC_VER >= 1700)
#define optional_CPP11_120 (optional_CPP11_OR_GREATER_ || optional_COMPILER_MSVC_VER >= 1800)
#define optional_CPP11_140 (optional_CPP11_OR_GREATER_ || optional_COMPILER_MSVC_VER >= 1900)
#define optional_CPP11_141 (optional_CPP11_OR_GREATER_ || optional_COMPILER_MSVC_VER >= 1910)
#define optional_CPP14_000 (optional_CPP14_OR_GREATER)
#define optional_CPP17_000 (optional_CPP17_OR_GREATER)
// clang >= 2.9, gcc >= 4.9, msvc >= vc14.0/1900 (vs15):
#define optional_CPP11_140_C290_G490 ((optional_CPP11_OR_GREATER_ && (optional_COMPILER_CLANG_VERSION >= 290 || optional_COMPILER_GNUC_VERSION >= 490)) || (optional_COMPILER_MSVC_VER >= 1900))
// clang >= 3.5, msvc >= vc11 (vs12):
#define optional_CPP11_110_C350 ( optional_CPP11_110 && !optional_BETWEEN( optional_COMPILER_CLANG_VERSION, 1, 350 ) )
// clang >= 3.5, gcc >= 5.0, msvc >= vc11 (vs12):
#define optional_CPP11_110_C350_G500 \
( optional_CPP11_110 && \
!( optional_BETWEEN( optional_COMPILER_CLANG_VERSION, 1, 350 ) \
|| optional_BETWEEN( optional_COMPILER_GNUC_VERSION , 1, 500 ) ) )
// Presence of C++11 language features:
#define optional_HAVE_CONSTEXPR_11 optional_CPP11_140
#define optional_HAVE_IS_DEFAULT optional_CPP11_140
#define optional_HAVE_NOEXCEPT optional_CPP11_140
#define optional_HAVE_NULLPTR optional_CPP11_100
#define optional_HAVE_REF_QUALIFIER optional_CPP11_140_C290_G490
#define optional_HAVE_STATIC_ASSERT optional_CPP11_110
#define optional_HAVE_INITIALIZER_LIST optional_CPP11_140
// Presence of C++14 language features:
#define optional_HAVE_CONSTEXPR_14 optional_CPP14_000
// Presence of C++17 language features:
#define optional_HAVE_NODISCARD optional_CPP17_000
// Presence of C++ library features:
#define optional_HAVE_CONDITIONAL optional_CPP11_120
#define optional_HAVE_REMOVE_CV optional_CPP11_120
#define optional_HAVE_TYPE_TRAITS optional_CPP11_90
#define optional_HAVE_TR1_TYPE_TRAITS (!! optional_COMPILER_GNUC_VERSION )
#define optional_HAVE_TR1_ADD_POINTER (!! optional_COMPILER_GNUC_VERSION )
#define optional_HAVE_IS_ASSIGNABLE optional_CPP11_110_C350
#define optional_HAVE_IS_MOVE_CONSTRUCTIBLE optional_CPP11_110_C350
#define optional_HAVE_IS_NOTHROW_MOVE_ASSIGNABLE optional_CPP11_110_C350
#define optional_HAVE_IS_NOTHROW_MOVE_CONSTRUCTIBLE optional_CPP11_110_C350
#define optional_HAVE_IS_TRIVIALLY_COPY_CONSTRUCTIBLE optional_CPP11_110_C350_G500
#define optional_HAVE_IS_TRIVIALLY_MOVE_CONSTRUCTIBLE optional_CPP11_110_C350_G500
// C++ feature usage:
#if optional_HAVE( CONSTEXPR_11 )
# define optional_constexpr constexpr
#else
# define optional_constexpr /*constexpr*/
#endif
#if optional_HAVE( IS_DEFAULT )
# define optional_is_default = default;
#else
# define optional_is_default {}
#endif
#if optional_HAVE( CONSTEXPR_14 )
# define optional_constexpr14 constexpr
#else
# define optional_constexpr14 /*constexpr*/
#endif
#if optional_HAVE( NODISCARD ) && !optional_CONFIG_NO_NODISCARD
# define optional_nodiscard [[nodiscard]]
#else
# define optional_nodiscard /*[[nodiscard]]*/
#endif
#if optional_HAVE( NOEXCEPT )
# define optional_noexcept noexcept
#else
# define optional_noexcept /*noexcept*/
#endif
#if optional_HAVE( NULLPTR )
# define optional_nullptr nullptr
#else
# define optional_nullptr NULL
#endif
#if optional_HAVE( REF_QUALIFIER )
// NOLINTNEXTLINE( bugprone-macro-parentheses )
# define optional_ref_qual &
# define optional_refref_qual &&
#else
# define optional_ref_qual /*&*/
# define optional_refref_qual /*&&*/
#endif
#if optional_HAVE( STATIC_ASSERT )
# define optional_static_assert(expr, text) static_assert(expr, text);
#else
# define optional_static_assert(expr, text) /*static_assert(expr, text);*/
#endif
// additional includes:
#if optional_CONFIG_NO_EXCEPTIONS
// already included:
#else
# include
#endif
#if optional_CPP11_OR_GREATER
# include
#endif
#if optional_HAVE( INITIALIZER_LIST )
# include
#endif
#if optional_HAVE( TYPE_TRAITS )
# include
#elif optional_HAVE( TR1_TYPE_TRAITS )
# include
#endif
// Method enabling
#if optional_CPP11_OR_GREATER
#define optional_REQUIRES_0(...) \
template< bool B = (__VA_ARGS__), typename std::enable_if::type = 0 >
#define optional_REQUIRES_T(...) \
, typename std::enable_if< (__VA_ARGS__), int >::type = 0
#define optional_REQUIRES_R(R, ...) \
typename std::enable_if< (__VA_ARGS__), R>::type
#define optional_REQUIRES_A(...) \
, typename std::enable_if< (__VA_ARGS__), void*>::type = nullptr
#endif
//
// optional:
//
namespace nonstd { namespace optional_lite {
namespace std11 {
template< class T, T v > struct integral_constant { enum { value = v }; };
template< bool B > struct bool_constant : integral_constant{};
typedef bool_constant< true > true_type;
typedef bool_constant< false > false_type;
#if optional_CPP11_OR_GREATER
using std::move;
#else
template< typename T > T & move( T & t ) { return t; }
#endif
#if optional_HAVE( CONDITIONAL )
using std::conditional;
#else
template< bool B, typename T, typename F > struct conditional { typedef T type; };
template< typename T, typename F > struct conditional { typedef F type; };
#endif // optional_HAVE_CONDITIONAL
#if optional_HAVE( IS_ASSIGNABLE )
using std::is_assignable;
#else
template< class T, class U > struct is_assignable : std11::true_type{};
#endif
#if optional_HAVE( IS_MOVE_CONSTRUCTIBLE )
using std::is_move_constructible;
#else
template< class T > struct is_move_constructible : std11::true_type{};
#endif
#if optional_HAVE( IS_NOTHROW_MOVE_ASSIGNABLE )
using std::is_nothrow_move_assignable;
#else
template< class T > struct is_nothrow_move_assignable : std11::true_type{};
#endif
#if optional_HAVE( IS_NOTHROW_MOVE_CONSTRUCTIBLE )
using std::is_nothrow_move_constructible;
#else
template< class T > struct is_nothrow_move_constructible : std11::true_type{};
#endif
#if optional_HAVE( IS_TRIVIALLY_COPY_CONSTRUCTIBLE )
using std::is_trivially_copy_constructible;
#else
template< class T > struct is_trivially_copy_constructible : std11::true_type{};
#endif
#if optional_HAVE( IS_TRIVIALLY_MOVE_CONSTRUCTIBLE )
using std::is_trivially_move_constructible;
#else
template< class T > struct is_trivially_move_constructible : std11::true_type{};
#endif
} // namespace std11
#if optional_CPP11_OR_GREATER
/// type traits C++17:
namespace std17 {
#if optional_CPP17_OR_GREATER
using std::is_swappable;
using std::is_nothrow_swappable;
#elif optional_CPP11_OR_GREATER
namespace detail {
using std::swap;
struct is_swappable
{
template< typename T, typename = decltype( swap( std::declval(), std::declval() ) ) >
static std11::true_type test( int /*unused*/ );
template< typename >
static std11::false_type test(...);
};
struct is_nothrow_swappable
{
// wrap noexcept(expr) in separate function as work-around for VC140 (VS2015):
template< typename T >
static constexpr bool satisfies()
{
return noexcept( swap( std::declval(), std::declval() ) );
}
template< typename T >
static auto test( int /*unused*/ ) -> std11::integral_constant{}
template< typename >
static auto test(...) -> std11::false_type;
};
} // namespace detail
// is [nothow] swappable:
template< typename T >
struct is_swappable : decltype( detail::is_swappable::test(0) ){};
template< typename T >
struct is_nothrow_swappable : decltype( detail::is_nothrow_swappable::test(0) ){};
#endif // optional_CPP17_OR_GREATER
} // namespace std17
/// type traits C++20:
namespace std20 {
template< typename T >
struct remove_cvref
{
typedef typename std::remove_cv< typename std::remove_reference::type >::type type;
};
} // namespace std20
#endif // optional_CPP11_OR_GREATER
/// class optional
template< typename T >
class optional;
namespace detail {
// C++11 emulation:
struct nulltype{};
template< typename Head, typename Tail >
struct typelist
{
typedef Head head;
typedef Tail tail;
};
#if optional_CONFIG_MAX_ALIGN_HACK
// Max align, use most restricted type for alignment:
#define optional_UNIQUE( name ) optional_UNIQUE2( name, __LINE__ )
#define optional_UNIQUE2( name, line ) optional_UNIQUE3( name, line )
#define optional_UNIQUE3( name, line ) name ## line
#define optional_ALIGN_TYPE( type ) \
type optional_UNIQUE( _t ); struct_t< type > optional_UNIQUE( _st )
template< typename T >
struct struct_t { T _; };
union max_align_t
{
optional_ALIGN_TYPE( char );
optional_ALIGN_TYPE( short int );
optional_ALIGN_TYPE( int );
optional_ALIGN_TYPE( long int );
optional_ALIGN_TYPE( float );
optional_ALIGN_TYPE( double );
optional_ALIGN_TYPE( long double );
optional_ALIGN_TYPE( char * );
optional_ALIGN_TYPE( short int * );
optional_ALIGN_TYPE( int * );
optional_ALIGN_TYPE( long int * );
optional_ALIGN_TYPE( float * );
optional_ALIGN_TYPE( double * );
optional_ALIGN_TYPE( long double * );
optional_ALIGN_TYPE( void * );
#ifdef HAVE_LONG_LONG
optional_ALIGN_TYPE( long long );
#endif
struct Unknown;
Unknown ( * optional_UNIQUE(_) )( Unknown );
Unknown * Unknown::* optional_UNIQUE(_);
Unknown ( Unknown::* optional_UNIQUE(_) )( Unknown );
struct_t< Unknown ( * )( Unknown) > optional_UNIQUE(_);
struct_t< Unknown * Unknown::* > optional_UNIQUE(_);
struct_t< Unknown ( Unknown::* )(Unknown) > optional_UNIQUE(_);
};
#undef optional_UNIQUE
#undef optional_UNIQUE2
#undef optional_UNIQUE3
#undef optional_ALIGN_TYPE
#elif defined( optional_CONFIG_ALIGN_AS ) // optional_CONFIG_MAX_ALIGN_HACK
// Use user-specified type for alignment:
#define optional_ALIGN_AS( unused ) \
optional_CONFIG_ALIGN_AS
#else // optional_CONFIG_MAX_ALIGN_HACK
// Determine POD type to use for alignment:
#define optional_ALIGN_AS( to_align ) \
typename type_of_size< alignment_types, alignment_of< to_align >::value >::type
template< typename T >
struct alignment_of;
template< typename T >
struct alignment_of_hack
{
char c;
T t;
alignment_of_hack();
};
template< size_t A, size_t S >
struct alignment_logic
{
enum { value = A < S ? A : S };
};
template< typename T >
struct alignment_of
{
enum { value = alignment_logic<
sizeof( alignment_of_hack ) - sizeof(T), sizeof(T) >::value };
};
template< typename List, size_t N >
struct type_of_size
{
typedef typename std11::conditional<
N == sizeof( typename List::head ),
typename List::head,
typename type_of_size::type >::type type;
};
template< size_t N >
struct type_of_size< nulltype, N >
{
typedef optional_CONFIG_ALIGN_AS_FALLBACK type;
};
template< typename T>
struct struct_t { T _; };
#define optional_ALIGN_TYPE( type ) \
typelist< type , typelist< struct_t< type >
struct Unknown;
typedef
optional_ALIGN_TYPE( char ),
optional_ALIGN_TYPE( short ),
optional_ALIGN_TYPE( int ),
optional_ALIGN_TYPE( long ),
optional_ALIGN_TYPE( float ),
optional_ALIGN_TYPE( double ),
optional_ALIGN_TYPE( long double ),
optional_ALIGN_TYPE( char *),
optional_ALIGN_TYPE( short * ),
optional_ALIGN_TYPE( int * ),
optional_ALIGN_TYPE( long * ),
optional_ALIGN_TYPE( float * ),
optional_ALIGN_TYPE( double * ),
optional_ALIGN_TYPE( long double * ),
optional_ALIGN_TYPE( Unknown ( * )( Unknown ) ),
optional_ALIGN_TYPE( Unknown * Unknown::* ),
optional_ALIGN_TYPE( Unknown ( Unknown::* )( Unknown ) ),
nulltype
> > > > > > > > > > > > > >
> > > > > > > > > > > > > >
> > > > > >
alignment_types;
#undef optional_ALIGN_TYPE
#endif // optional_CONFIG_MAX_ALIGN_HACK
/// C++03 constructed union to hold value.
template< typename T >
union storage_t
{
//private:
// template< typename > friend class optional;
typedef T value_type;
storage_t() optional_is_default
explicit storage_t( value_type const & v )
{
construct_value( v );
}
void construct_value( value_type const & v )
{
::new( value_ptr() ) value_type( v );
}
#if optional_CPP11_OR_GREATER
explicit storage_t( value_type && v )
{
construct_value( std::move( v ) );
}
void construct_value( value_type && v )
{
::new( const_cast(static_cast(value_ptr())) ) value_type( std::move( v ) );
}
template< class... Args >
storage_t( nonstd_lite_in_place_t(T), Args&&... args )
{
emplace( std::forward(args)... );
}
template< class... Args >
void emplace( Args&&... args )
{
::new( const_cast(static_cast(value_ptr())) ) value_type( std::forward(args)... );
}
template< class U, class... Args >
void emplace( std::initializer_list il, Args&&... args )
{
::new( const_cast(static_cast(value_ptr())) ) value_type( il, std::forward(args)... );
}
#endif
void destruct_value()
{
value_ptr()->~T();
}
optional_nodiscard value_type const * value_ptr() const
{
return as();
}
value_type * value_ptr()
{
return as();
}
optional_nodiscard value_type const & value() const optional_ref_qual
{
return * value_ptr();
}
value_type & value() optional_ref_qual
{
return * value_ptr();
}
#if optional_HAVE( REF_QUALIFIER )
optional_nodiscard value_type const && value() const optional_refref_qual
{
return std::move( value() );
}
value_type && value() optional_refref_qual
{
return std::move( value() );
}
#endif
#if optional_CPP11_OR_GREATER
using aligned_storage_t = typename std::aligned_storage< sizeof(value_type), alignof(value_type) >::type;
aligned_storage_t data;
#elif optional_CONFIG_MAX_ALIGN_HACK
typedef struct { unsigned char data[ sizeof(value_type) ]; } aligned_storage_t;
max_align_t hack;
aligned_storage_t data;
#else
typedef optional_ALIGN_AS(value_type) align_as_type;
typedef struct { align_as_type data[ 1 + ( sizeof(value_type) - 1 ) / sizeof(align_as_type) ]; } aligned_storage_t;
aligned_storage_t data;
# undef optional_ALIGN_AS
#endif // optional_CONFIG_MAX_ALIGN_HACK
optional_nodiscard void * ptr() optional_noexcept
{
return &data;
}
optional_nodiscard void const * ptr() const optional_noexcept
{
return &data;
}
template
optional_nodiscard U * as()
{
return reinterpret_cast( ptr() );
}
template
optional_nodiscard U const * as() const
{
return reinterpret_cast( ptr() );
}
};
} // namespace detail
/// disengaged state tag
struct nullopt_t
{
struct init{};
explicit optional_constexpr nullopt_t( init /*unused*/ ) optional_noexcept {}
};
#if optional_HAVE( CONSTEXPR_11 )
constexpr nullopt_t nullopt{ nullopt_t::init{} };
#else
// extra parenthesis to prevent the most vexing parse:
const nullopt_t nullopt(( nullopt_t::init() ));
#endif
/// optional access error
#if ! optional_CONFIG_NO_EXCEPTIONS
class optional_nodiscard bad_optional_access : public std::logic_error
{
public:
explicit bad_optional_access()
: logic_error( "bad optional access" ) {}
};
#endif //optional_CONFIG_NO_EXCEPTIONS
/// optional
template< typename T>
class optional
{
optional_static_assert(( !std::is_same::value ),
"T in optional must not be of type 'nullopt_t'.")
optional_static_assert(( !std::is_same::value ),
"T in optional must not be of type 'in_place_t'.")
optional_static_assert(( std::is_object::value && std::is_destructible::value && !std::is_array::value ),
"T in optional must meet the Cpp17Destructible requirements.")
private:
template< typename > friend class optional;
typedef void (optional::*safe_bool)() const;
public:
typedef T value_type;
// x.x.3.1, constructors
// 1a - default construct
optional_constexpr optional() optional_noexcept
: has_value_( false )
, contained()
{}
// 1b - construct explicitly empty
// NOLINTNEXTLINE( google-explicit-constructor, hicpp-explicit-conversions )
optional_constexpr optional( nullopt_t /*unused*/ ) optional_noexcept
: has_value_( false )
, contained()
{}
// 2 - copy-construct
#if optional_CPP11_OR_GREATER
// template< typename U = T
// optional_REQUIRES_T(
// std::is_copy_constructible::value
// || std11::is_trivially_copy_constructible::value
// )
// >
#endif
optional_constexpr14 optional( optional const & other )
: has_value_( other.has_value() )
{
if ( other.has_value() )
{
contained.construct_value( other.contained.value() );
}
}
#if optional_CPP11_OR_GREATER
// 3 (C++11) - move-construct from optional
template< typename U = T
optional_REQUIRES_T(
std11::is_move_constructible::value
|| std11::is_trivially_move_constructible::value
)
>
optional_constexpr14 optional( optional && other )
// NOLINTNEXTLINE( performance-noexcept-move-constructor )
noexcept( std11::is_nothrow_move_constructible::value )
: has_value_( other.has_value() )
{
if ( other.has_value() )
{
contained.construct_value( std::move( other.contained.value() ) );
}
}
// 4a (C++11) - explicit converting copy-construct from optional
template< typename U
optional_REQUIRES_T(
std::is_constructible::value
&& !std::is_constructible::value
&& !std::is_constructible::value
&& !std::is_constructible::value
&& !std::is_constructible::value
&& !std::is_convertible< optional & , T>::value
&& !std::is_convertible< optional && , T>::value
&& !std::is_convertible< optional const & , T>::value
&& !std::is_convertible< optional const &&, T>::value
&& !std::is_convertible< U const & , T>::value /*=> explicit */
)
>
explicit optional( optional const & other )
: has_value_( other.has_value() )
{
if ( other.has_value() )
{
contained.construct_value( T{ other.contained.value() } );
}
}
#endif // optional_CPP11_OR_GREATER
// 4b (C++98 and later) - non-explicit converting copy-construct from optional
template< typename U
#if optional_CPP11_OR_GREATER
optional_REQUIRES_T(
std::is_constructible::value
&& !std::is_constructible::value
&& !std::is_constructible::value
&& !std::is_constructible::value
&& !std::is_constructible::value
&& !std::is_convertible< optional & , T>::value
&& !std::is_convertible< optional && , T>::value
&& !std::is_convertible< optional const & , T>::value
&& !std::is_convertible< optional const &&, T>::value
&& std::is_convertible< U const & , T>::value /*=> non-explicit */
)
#endif // optional_CPP11_OR_GREATER
>
// NOLINTNEXTLINE( google-explicit-constructor, hicpp-explicit-conversions )
/*non-explicit*/ optional( optional const & other )
: has_value_( other.has_value() )
{
if ( other.has_value() )
{
contained.construct_value( other.contained.value() );
}
}
#if optional_CPP11_OR_GREATER
// 5a (C++11) - explicit converting move-construct from optional
template< typename U
optional_REQUIRES_T(
std::is_constructible::value
&& !std::is_constructible::value
&& !std::is_constructible::value
&& !std::is_constructible::value
&& !std::is_constructible::value
&& !std::is_convertible< optional & , T>::value
&& !std::is_convertible< optional && , T>::value
&& !std::is_convertible< optional const & , T>::value
&& !std::is_convertible< optional const &&, T>::value
&& !std::is_convertible< U &&, T>::value /*=> explicit */
)
>
explicit optional( optional && other
)
: has_value_( other.has_value() )
{
if ( other.has_value() )
{
contained.construct_value( T{ std::move( other.contained.value() ) } );
}
}
// 5a (C++11) - non-explicit converting move-construct from optional
template< typename U
optional_REQUIRES_T(
std::is_constructible::value
&& !std::is_constructible::value
&& !std::is_constructible::value
&& !std::is_constructible::value
&& !std::is_constructible::value
&& !std::is_convertible< optional & , T>::value
&& !std::is_convertible< optional && , T>::value
&& !std::is_convertible< optional const & , T>::value
&& !std::is_convertible< optional const &&, T>::value
&& std::is_convertible< U &&, T>::value /*=> non-explicit */
)
>
// NOLINTNEXTLINE( google-explicit-constructor, hicpp-explicit-conversions )
/*non-explicit*/ optional( optional && other )
: has_value_( other.has_value() )
{
if ( other.has_value() )
{
contained.construct_value( std::move( other.contained.value() ) );
}
}
// 6 (C++11) - in-place construct
template< typename... Args
optional_REQUIRES_T(
std::is_constructible::value
)
>
optional_constexpr explicit optional( nonstd_lite_in_place_t(T), Args&&... args )
: has_value_( true )
, contained( in_place, std::forward(args)... )
{}
// 7 (C++11) - in-place construct, initializer-list
template< typename U, typename... Args
optional_REQUIRES_T(
std::is_constructible::value
)
>
optional_constexpr explicit optional( nonstd_lite_in_place_t(T), std::initializer_list il, Args&&... args )
: has_value_( true )
, contained( T( il, std::forward(args)...) )
{}
// 8a (C++11) - explicit move construct from value
template< typename U = T
optional_REQUIRES_T(
std::is_constructible::value
&& !std::is_same::value
&& !std::is_same::value
&& !std::is_convertible::value /*=> explicit */
)
>
optional_constexpr explicit optional( U && value )
: has_value_( true )
, contained( nonstd_lite_in_place(T), std::forward( value ) )
{}
// 8b (C++11) - non-explicit move construct from value
template< typename U = T
optional_REQUIRES_T(
std::is_constructible::value
&& !std::is_same::value
&& !std::is_same::value
&& std::is_convertible::value /*=> non-explicit */
)
>
// NOLINTNEXTLINE( google-explicit-constructor, hicpp-explicit-conversions )
optional_constexpr /*non-explicit*/ optional( U && value )
: has_value_( true )
, contained( nonstd_lite_in_place(T), std::forward( value ) )
{}
#else // optional_CPP11_OR_GREATER
// 8 (C++98)
optional( value_type const & value )
: has_value_( true )
, contained( value )
{}
#endif // optional_CPP11_OR_GREATER
// x.x.3.2, destructor
~optional()
{
if ( has_value() )
{
contained.destruct_value();
}
}
// x.x.3.3, assignment
// 1 (C++98and later) - assign explicitly empty
optional & operator=( nullopt_t /*unused*/) optional_noexcept
{
reset();
return *this;
}
// 2 (C++98and later) - copy-assign from optional
#if optional_CPP11_OR_GREATER
// NOLINTNEXTLINE( cppcoreguidelines-c-copy-assignment-signature, misc-unconventional-assign-operator )
optional_REQUIRES_R(
optional &,
true
// std::is_copy_constructible::value
// && std::is_copy_assignable::value
)
operator=( optional const & other )
noexcept(
std11::is_nothrow_move_assignable::value
&& std11::is_nothrow_move_constructible::value
)
#else
optional & operator=( optional const & other )
#endif
{
if ( (has_value() == true ) && (other.has_value() == false) ) { reset(); }
else if ( (has_value() == false) && (other.has_value() == true ) ) { initialize( *other ); }
else if ( (has_value() == true ) && (other.has_value() == true ) ) { contained.value() = *other; }
return *this;
}
#if optional_CPP11_OR_GREATER
// 3 (C++11) - move-assign from optional
// NOLINTNEXTLINE( cppcoreguidelines-c-copy-assignment-signature, misc-unconventional-assign-operator )
optional_REQUIRES_R(
optional &,
true
// std11::is_move_constructible::value
// && std::is_move_assignable::value
)
operator=( optional && other ) noexcept
{
if ( (has_value() == true ) && (other.has_value() == false) ) { reset(); }
else if ( (has_value() == false) && (other.has_value() == true ) ) { initialize( std::move( *other ) ); }
else if ( (has_value() == true ) && (other.has_value() == true ) ) { contained.value() = std::move( *other ); }
return *this;
}
// 4 (C++11) - move-assign from value
template< typename U = T >
// NOLINTNEXTLINE( cppcoreguidelines-c-copy-assignment-signature, misc-unconventional-assign-operator )
optional_REQUIRES_R(
optional &,
std::is_constructible::value
&& std11::is_assignable::value
&& !std::is_same::value
&& !std::is_same::value
&& !(std::is_scalar::value && std::is_same::value)
)
operator=( U && value )
{
if ( has_value() )
{
contained.value() = std::forward( value );
}
else
{
initialize( T( std::forward( value ) ) );
}
return *this;
}
#else // optional_CPP11_OR_GREATER
// 4 (C++98) - copy-assign from value
template< typename U /*= T*/ >
optional & operator=( U const & value )
{
if ( has_value() ) contained.value() = value;
else initialize( T( value ) );
return *this;
}
#endif // optional_CPP11_OR_GREATER
// 5 (C++98 and later) - converting copy-assign from optional
template< typename U >
#if optional_CPP11_OR_GREATER
// NOLINTNEXTLINE( cppcoreguidelines-c-copy-assignment-signature, misc-unconventional-assign-operator )
optional_REQUIRES_R(
optional&,
std::is_constructible< T , U const &>::value
&& std11::is_assignable< T&, U const &>::value
&& !std::is_constructible::value
&& !std::is_constructible::value
&& !std::is_constructible::value
&& !std::is_constructible::value
&& !std::is_convertible< optional & , T>::value
&& !std::is_convertible< optional && , T>::value
&& !std::is_convertible< optional const & , T>::value
&& !std::is_convertible< optional const &&, T>::value
&& !std11::is_assignable< T&, optional & >::value
&& !std11::is_assignable< T&, optional && >::value
&& !std11::is_assignable< T&, optional const & >::value
&& !std11::is_assignable< T&, optional const && >::value
)
#else
optional&
#endif // optional_CPP11_OR_GREATER
operator=( optional const & other )
{
return *this = optional( other );
}
#if optional_CPP11_OR_GREATER
// 6 (C++11) - converting move-assign from optional
template< typename U >
// NOLINTNEXTLINE( cppcoreguidelines-c-copy-assignment-signature, misc-unconventional-assign-operator )
optional_REQUIRES_R(
optional&,
std::is_constructible< T , U>::value
&& std11::is_assignable< T&, U>::value
&& !std::is_constructible::value
&& !std::is_constructible::value
&& !std::is_constructible::value
&& !std::is_constructible::value
&& !std::is_convertible< optional & , T>::value
&& !std::is_convertible< optional && , T>::value
&& !std::is_convertible< optional const & , T>::value
&& !std::is_convertible< optional const &&, T>::value
&& !std11::is_assignable< T&, optional & >::value
&& !std11::is_assignable< T&, optional && >::value
&& !std11::is_assignable< T&, optional const & >::value
&& !std11::is_assignable< T&, optional const && >::value
)
operator=( optional && other )
{
return *this = optional( std::move( other ) );
}
// 7 (C++11) - emplace
template< typename... Args
optional_REQUIRES_T(
std::is_constructible::value
)
>
T& emplace( Args&&... args )
{
*this = nullopt;
contained.emplace( std::forward(args)... );
has_value_ = true;
return contained.value();
}
// 8 (C++11) - emplace, initializer-list
template< typename U, typename... Args
optional_REQUIRES_T(
std::is_constructible::value
)
>
T& emplace( std::initializer_list il, Args&&... args )
{
*this = nullopt;
contained.emplace( il, std::forward(args)... );
has_value_ = true;
return contained.value();
}
#endif // optional_CPP11_OR_GREATER
// x.x.3.4, swap
void swap( optional & other )
#if optional_CPP11_OR_GREATER
noexcept(
std11::is_nothrow_move_constructible::value
&& std17::is_nothrow_swappable::value
)
#endif
{
using std::swap;
if ( (has_value() == true ) && (other.has_value() == true ) ) { swap( **this, *other ); }
else if ( (has_value() == false) && (other.has_value() == true ) ) { initialize( std11::move(*other) ); other.reset(); }
else if ( (has_value() == true ) && (other.has_value() == false) ) { other.initialize( std11::move(**this) ); reset(); }
}
// x.x.3.5, observers
optional_constexpr value_type const * operator ->() const
{
return assert( has_value() ),
contained.value_ptr();
}
optional_constexpr14 value_type * operator ->()
{
return assert( has_value() ),
contained.value_ptr();
}
optional_constexpr value_type const & operator *() const optional_ref_qual
{
return assert( has_value() ),
contained.value();
}
optional_constexpr14 value_type & operator *() optional_ref_qual
{
return assert( has_value() ),
contained.value();
}
#if optional_HAVE( REF_QUALIFIER )
optional_constexpr value_type const && operator *() const optional_refref_qual
{
return std::move( **this );
}
optional_constexpr14 value_type && operator *() optional_refref_qual
{
return std::move( **this );
}
#endif
#if optional_CPP11_OR_GREATER
optional_constexpr explicit operator bool() const optional_noexcept
{
return has_value();
}
#else
optional_constexpr operator safe_bool() const optional_noexcept
{
return has_value() ? &optional::this_type_does_not_support_comparisons : 0;
}
#endif
// NOLINTNEXTLINE( modernize-use-nodiscard )
/*optional_nodiscard*/ optional_constexpr bool has_value() const optional_noexcept
{
return has_value_;
}
// NOLINTNEXTLINE( modernize-use-nodiscard )
/*optional_nodiscard*/ optional_constexpr14 value_type const & value() const optional_ref_qual
{
#if optional_CONFIG_NO_EXCEPTIONS
assert( has_value() );
#else
if ( ! has_value() )
{
throw bad_optional_access();
}
#endif
return contained.value();
}
optional_constexpr14 value_type & value() optional_ref_qual
{
#if optional_CONFIG_NO_EXCEPTIONS
assert( has_value() );
#else
if ( ! has_value() )
{
throw bad_optional_access();
}
#endif
return contained.value();
}
#if optional_HAVE( REF_QUALIFIER ) && ( !optional_COMPILER_GNUC_VERSION || optional_COMPILER_GNUC_VERSION >= 490 )
// NOLINTNEXTLINE( modernize-use-nodiscard )
/*optional_nodiscard*/ optional_constexpr value_type const && value() const optional_refref_qual
{
return std::move( value() );
}
optional_constexpr14 value_type && value() optional_refref_qual
{
return std::move( value() );
}
#endif
#if optional_HAVE( REF_QUALIFIER )
template< typename U >
optional_constexpr value_type value_or( U && v ) const optional_ref_qual
{
return has_value() ? contained.value() : static_cast(std::forward( v ) );
}
template< typename U >
optional_constexpr14 value_type value_or( U && v ) optional_refref_qual
{
#if optional_COMPILER_CLANG_VERSION
return has_value() ? /*std::move*/( contained.value() ) : static_cast(std::forward( v ) );
#else
return has_value() ? std::move( contained.value() ) : static_cast(std::forward( v ) );
#endif
}
#else
template< typename U >
optional_constexpr value_type value_or( U const & v ) const
{
return has_value() ? contained.value() : static_cast( v );
}
#endif // optional_HAVE( REF_QUALIFIER )
#if !optional_CONFIG_NO_EXTENSIONS
#if optional_HAVE( REF_QUALIFIER )
template< typename F >
optional_constexpr value_type value_or_eval( F f ) const &
{
return has_value() ? contained.value() : f();
}
template< typename F >
optional_constexpr14 value_type value_or_eval( F f ) &&
{
if ( has_value() )
{
return std::move( contained.value() );
}
else
{
return f();
}
}
#else
template< typename F >
optional_constexpr value_type value_or_eval( F f ) const
{
return has_value() ? contained.value() : f();
}
#endif // optional_HAVE( REF_QUALIFIER )
#endif // !optional_CONFIG_NO_EXTENSIONS
// x.x.3.6, modifiers
void reset() optional_noexcept
{
if ( has_value() )
{
contained.destruct_value();
}
has_value_ = false;
}
private:
void this_type_does_not_support_comparisons() const {}
template< typename V >
void initialize( V const & value )
{
assert( ! has_value() );
contained.construct_value( value );
has_value_ = true;
}
#if optional_CPP11_OR_GREATER
template< typename V >
void initialize( V && value )
{
assert( ! has_value() );
contained.construct_value( std::forward( value ) );
has_value_ = true;
}
#endif
private:
bool has_value_;
detail::storage_t< value_type > contained;
};
// Relational operators
template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator==( optional const & x, optional const & y )
{
return bool(x) != bool(y) ? false : !bool( x ) ? true : *x == *y;
}
template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator!=( optional const & x, optional const & y )
{
return !(x == y);
}
template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator
optional_nodiscard optional_constexpr bool operator>( optional const & x, optional const & y )
{
return (y < x);
}
template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator
optional_nodiscard optional_constexpr bool operator>=( optional const & x, optional const & y )
{
return !(x < y);
}
// Comparison with nullopt
template< typename T >
optional_nodiscard optional_constexpr bool operator==( optional const & x, nullopt_t /*unused*/ ) optional_noexcept
{
return (!x);
}
template< typename T >
optional_nodiscard optional_constexpr bool operator==( nullopt_t /*unused*/, optional const & x ) optional_noexcept
{
return (!x);
}
template< typename T >
optional_nodiscard optional_constexpr bool operator!=( optional const & x, nullopt_t /*unused*/ ) optional_noexcept
{
return bool(x);
}
template< typename T >
optional_nodiscard optional_constexpr bool operator!=( nullopt_t /*unused*/, optional const & x ) optional_noexcept
{
return bool(x);
}
template< typename T >
optional_nodiscard optional_constexpr bool operator
optional_nodiscard optional_constexpr bool operator
optional_nodiscard optional_constexpr bool operator
optional_nodiscard optional_constexpr bool operator
optional_nodiscard optional_constexpr bool operator>( optional const & x, nullopt_t /*unused*/ ) optional_noexcept
{
return bool(x);
}
template< typename T >
optional_nodiscard optional_constexpr bool operator>( nullopt_t /*unused*/, optional const & /*unused*/ ) optional_noexcept
{
return false;
}
template< typename T >
optional_nodiscard optional_constexpr bool operator>=( optional const & /*unused*/, nullopt_t /*unused*/ ) optional_noexcept
{
return true;
}
template< typename T >
optional_nodiscard optional_constexpr bool operator>=( nullopt_t /*unused*/, optional const & x ) optional_noexcept
{
return (!x);
}
// Comparison with T
template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator==( optional const & x, U const & v )
{
return bool(x) ? *x == v : false;
}
template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator==( U const & v, optional const & x )
{
return bool(x) ? v == *x : false;
}
template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator!=( optional const & x, U const & v )
{
return bool(x) ? *x != v : true;
}
template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator!=( U const & v, optional const & x )
{
return bool(x) ? v != *x : true;
}
template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator
optional_nodiscard optional_constexpr bool operator
optional_nodiscard optional_constexpr bool operator v : false;
}
template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator>( U const & v, optional const & x )
{
return bool(x) ? v > *x : true;
}
template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator>=( optional const & x, U const & v )
{
return bool(x) ? *x >= v : false;
}
template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator>=( U const & v, optional const & x )
{
return bool(x) ? v >= *x : true;
}
// Specialized algorithms
template< typename T
#if optional_CPP11_OR_GREATER
optional_REQUIRES_T(
std11::is_move_constructible::value
&& std17::is_swappable::value )
#endif
>
void swap( optional & x, optional & y )
#if optional_CPP11_OR_GREATER
noexcept( noexcept( x.swap(y) ) )
#endif
{
x.swap( y );
}
#if optional_CPP11_OR_GREATER
template< typename T >
optional_constexpr optional< typename std::decay::type > make_optional( T && value )
{
return optional< typename std::decay::type >( std::forward( value ) );
}
template< typename T, typename...Args >
optional_constexpr optional make_optional( Args&&... args )
{
return optional( nonstd_lite_in_place(T), std::forward(args)...);
}
template< typename T, typename U, typename... Args >
optional_constexpr optional make_optional( std::initializer_list il, Args&&... args )
{
return optional( nonstd_lite_in_place(T), il, std::forward(args)...);
}
#else
template< typename T >
optional make_optional( T const & value )
{
return optional( value );
}
#endif // optional_CPP11_OR_GREATER
} // namespace optional_lite
using optional_lite::optional;
using optional_lite::nullopt_t;
using optional_lite::nullopt;
#if ! optional_CONFIG_NO_EXCEPTIONS
using optional_lite::bad_optional_access;
#endif
using optional_lite::make_optional;
} // namespace nonstd
#if optional_CPP11_OR_GREATER
// specialize the std::hash algorithm:
namespace std {
template< class T >
struct hash< nonstd::optional >
{
public:
std::size_t operator()( nonstd::optional const & v ) const optional_noexcept
{
return bool( v ) ? std::hash{}( *v ) : 0;
}
};
} //namespace std
#endif // optional_CPP11_OR_GREATER
#if defined(__clang__)
# pragma clang diagnostic pop
#elif defined(__GNUC__)
# pragma GCC diagnostic pop
#elif defined(_MSC_VER )
# pragma warning( pop )
#endif
#endif // optional_USES_STD_OPTIONAL
#endif // NONSTD_OPTIONAL_LITE_HPP