This class is a replacement for C++17 std::variant. More...

#include <cvb/shims/variant.hpp>

Public Member Functions
	variant () noexcept
	Default ctor creating a variant with default value of the first alternative type.

	~variant () noexcept
	Destructor.

	variant (const variant &rhs)
	Copy ctor. More...

	variant (variant &&rhs)
	Move ctor. More...

variant &	operator= (const variant &rhs)
	Copy operator. More...

variant &	operator= (variant &&rhs)
	Move operator. More...

template<class T , typename std::enable_if<!std::is_same< T, variant & >::value, int >::type = 0>
	variant (T &&value)
	Ctor from an object of supported type `T`. More...

template<class T , typename std::enable_if<!std::is_same< T, variant & >::value, int >::type = 0>
variant &	operator= (T &&value)
	Assignment from an object of supported type `T`. More...

template<size_t I, class... ARGS>
variant_alternative< I, variant< TS... > >::type &	emplace (ARGS &&... args)
	Emplaces an object as alternative at index `I`. More...

template<class T , class... ARGS>
T &	emplace (ARGS &&... args)
	Emplaces an object as a type `T`. More...

size_t	index () const noexcept
	Gets the zero-based index of the alternative held by this instance.

void	swap (variant &other)
	Swaps the content of this variant with the other one. More...

bool	valueless_by_exception () const noexcept
	Returns false only if this instance holds a value. More...

Related Functions
(Note that these are not member functions.)
template<class T >
static const constexpr size_t	variant_alternatives_size_v = variant_size<T>::value
	Get the number of alternatives in a variant.

template<size_t I, class... TS>
const variant_alternative_t< I, variant< TS... > > &	get (const variant< TS... > &var)
	Gets the value of the given variant var as the alternative with index `I`. More...

template<class T , class... TS>
const T &	get (const variant< TS... > &var)
	Gets the value of the given variant var as the alternative with type `T`. More...

template<size_t I, class... TS>
std::add_pointer< constvariant_alternative_t< I, variant< TS... > > >::type	get_if (const variant< TS... > *pvar) noexcept
	Tries to get the value of the given variant pointer pvar as the alternative with index `I`. More...

template<class T , class... TS>
std::add_pointer< constT >::type	get_if (const variant< TS... > *pvar) noexcept
	Tries to get the value of the given variant pointer pvar as the alternative with type `T`. More...

template<class T , class... TS>
bool	holds_alternative (const variant< TS... > &var) noexcept
	Gets whether the variant var holds an instance of type `T`. More...

template<class VISITOR , class VARIANT >
auto	visit (VISITOR &&visitor, VARIANT &&var) -> decltype(visitor(get< 0 >(var)))
	Visits the given variant var. Cvb::Shims::visit can only visit one variant (not multiple like std::visit). More...

template<class... TS>
bool	operator== (const variant< TS... > &lhs, const variant< TS... > &rhs)
	Equality operator for variant objects. More...

template<class... TS>
bool	operator!= (const variant< TS... > &lhs, const variant< TS... > &rhs)
	Inequality operator for variant objects. More...

template<class... TS>
bool	operator< (const variant< TS... > &lhs, const variant< TS... > &rhs)
	Less than operator for variant objects. More...

template<class... TS>
bool	operator<= (const variant< TS... > &lhs, const variant< TS... > &rhs)
	Less-than or equal operator for variant object. More...

template<class... TS>
bool	operator> (const variant< TS... > &lhs, const variant< TS... > &rhs)
	Greater-than operator for variant object. More...

template<class... TS>
bool	operator>= (const variant< TS... > &lhs, const variant< TS... > &rhs)
	Greater-than or equal operator for variant object. More...

Detailed Description

template<class... TS>
class Cvb::Shims::variant< TS >

This class is a replacement for C++17 std::variant.

Constructor & Destructor Documentation

◆ variant() [1/3]

variant ( const variant< TS > & rhs )

Copy ctor.

Parameters

[in] rhs Object to copy.

◆ variant() [2/3]

variant ( variant< TS > && rhs )

Move ctor.

Parameters

[in] rhs Object to move.

◆ variant() [3/3]

variant ( T && value )

inline

Ctor from an object of supported type T.

Template Parameters

T	Type of value to set.

Parameters

[in] value The value to store in this variant.

Member Function Documentation

◆ emplace() [1/2]

variant_alternative< I, variant< TS... > >::type & emplace ( ARGS &&... args )

Emplaces an object as alternative at index I.

Template Parameters

I	Index of alternative to use.

Parameters

[in] args Arguments to be forwarded to alternative's ctor.

Returns: Reference to the newly created type.

◆ emplace() [2/2]

T & emplace ( ARGS &&... args )

inline

Emplaces an object as a type T.

Template Parameters

T	Type of alternative to use.

Parameters

[in] args Arguments to be forwarded to alternative's ctor.

Returns: Reference to the newly created type.

◆ operator=() [1/3]

variant< TS... > & operator= ( const variant< TS > & rhs )

Copy operator.

Parameters

[in] rhs Object to copy.

Returns: Reference to this object.

◆ operator=() [2/3]

variant & operator= ( T && value )

inline

Assignment from an object of supported type T.

Note: If assignment of the value fails this instance is in invalid state. I.e. valueless_by_exception() returns true.

Template Parameters

T	Type of value to set.

Parameters

[in] value The value to store in this variant.

Returns: Reference to this object.

◆ operator=() [3/3]

variant< TS... > & operator= ( variant< TS > && rhs )

Move operator.

Parameters

[in] rhs Object to move.

Returns: Reference to this object.

◆ swap()

void swap ( variant< TS > & other )

Swaps the content of this variant with the other one.

Parameters

[in] other Other object to swap content with.

◆ valueless_by_exception()

bool valueless_by_exception ( ) const

inlinenoexcept

Returns false only if this instance holds a value.

Returns: false if this instance holds a value; true otherwise.

Friends And Related Function Documentation

◆ get() [1/2]

const variant_alternative_t< I, variant< TS... > > & get ( const variant< TS... > & var )

Template Parameters

I	Index of alternative to extract.

Parameters

[in] var Variant to get the value of.

Returns: Reference to the value in var.

Exceptions

bad_variant_access thrown if I is unequal variant::index().

◆ get() [2/2]

const T & get ( const variant< TS... > & var )

Template Parameters

T	Type to query.

Parameters

[in] var Variant to get the value of.

Returns: Reference to the value in var.

Exceptions

bad_variant_access thrown if T is not a variant alternative.

◆ get_if() [1/2]

std::add_pointer< constvariant_alternative_t< I, variant< TS... > > >::type get_if ( const variant< TS... > * pvar )

Template Parameters

I	Index of alternative to extract.

Parameters

[in] pvar Variant to get the value of.

Returns: Pointer to the value in pvar; nullptr if pvar is nullptr or I is unequal pvar object's index().

◆ get_if() [2/2]

std::add_pointer< constT >::type get_if ( const variant< TS... > * pvar )

Template Parameters

T	Type to query.

Parameters

[in] pvar Variant to get the value of.

Returns: Pointer to the value in pvar; nullptr if pvar is nullptr or if the stored alternative is not of type T.

◆ holds_alternative()

bool holds_alternative ( const variant< TS... > & var )

Template Parameters

T	Type to test.

Parameters

[in] var Variant to check.

Returns: true if var currently holds a type T; false if not.

◆ operator!=()

bool operator!=	(	const variant< TS... > &	lhs,
		const variant< TS... > &	rhs
	)

Parameters

[in]	lhs	Left hand side object.
[in]	rhs	Right hand side object.

Returns: true if both object store the same variant::index() or if they are both not variant::valueless_by_exception and the actual values are unequal.

◆ operator<()

bool operator<	(	const variant< TS... > &	lhs,
		const variant< TS... > &	rhs
	)

Parameters

[in]	lhs	Left hand side object.
[in]	rhs	Right hand side object.

Returns

false if rhs is variant::valueless_by_exception()
true if lhs is variant::valueless_by_exception()
true if lhs variant::index() is less than the rhs one.
false if lhs variant::index() is greater than the rhs one.
in the end the actual values are less-than compared.

◆ operator<=()

bool operator<=	(	const variant< TS... > &	lhs,
		const variant< TS... > &	rhs
	)

Parameters

[in]	lhs	Left hand side object.
[in]	rhs	Right hand side object.

Returns: Not rhs less-than lhs comparison.

◆ operator==()

bool operator==	(	const variant< TS... > &	lhs,
		const variant< TS... > &	rhs
	)

Parameters

[in]	lhs	Left hand side object.
[in]	rhs	Right hand side object.

Returns: true if both objects store the same variant::index() and if they are both variant::valueless_by_exception() or the actual values are equal.

◆ operator>()

bool operator>	(	const variant< TS... > &	lhs,
		const variant< TS... > &	rhs
	)

Parameters

[in]	lhs	Left hand side object.
[in]	rhs	Right hand side object.

Returns: rhs less-than lhs comparison.

◆ operator>=()

bool operator>=	(	const variant< TS... > &	lhs,
		const variant< TS... > &	rhs
	)

Parameters

[in]	lhs	Left hand side object.
[in]	rhs	Right hand side object.

Returns: Not lhs less-than rhs comparison.

◆ visit()

auto visit	(	VISITOR &&	visitor,
		VARIANT &&	var
	)		-> decltype(visitor(get<0>(var)))

Template Parameters

VISITOR	Callable that get the value of the variant as argument.
TS	Parameter pack of the variant alternatives.

Parameters

[in]	visitor	Callable to visit the variant var.
[in]	var	Variant to visit.

Returns: Type depends on visitor.

Public Member Functions

Related Functions

Detailed Description

Constructor & Destructor Documentation

◆ variant() [1/3]

◆ variant() [2/3]

◆ variant() [3/3]

Member Function Documentation

◆ emplace() [1/2]

◆ emplace() [2/2]

◆ operator=() [1/3]

◆ operator=() [2/3]

◆ operator=() [3/3]

◆ swap()

◆ valueless_by_exception()

Friends And Related Function Documentation

◆ get() [1/2]

◆ get() [2/2]

◆ get_if() [1/2]

◆ get_if() [2/2]

◆ holds_alternative()

◆ operator!=()

◆ operator<()

◆ operator<=()

◆ operator==()

◆ operator>()

◆ operator>=()

◆ visit()