atria::variant Namespace Reference

Tools for better usability of boost::variant, eggs::variant and potentially other implementations of sum types. More...

Classes
struct	otherwise_t
	Wraps a functor such that it has a fixed return value. More...
struct	variant_types
	Metafunction that for a given type T, returns a meta::pack containing the list of types that can be held in the variant. More...
struct	variant_types_impl
	Given an unqualified variant type T, returns a meta::pack with the alternatives in the variant. More...
struct	variant_types_impl< boost::variant< T, Ts... > >
struct	variant_types_impl< eggs::variants::variant< Ts... > >
struct	variant_types_impl< meta::pack< Ts... > >
struct	visitor_result_of
struct	visitor_result_of< FnT, meta::pack< VariantTs... > >
class	visitor_t
	General visitor based on a set of function objects. More...
struct	when_t
	Wraps a functor such that it has a fixed argument list. More...

Typedefs
using	eggs_t = meta::copy_decay_t< VariantT, meta::unpack< eggs::variant, variant_types_t< estd::decay_t< VariantT > > > >
template<typename FnT , typename... VariantTs>
using	visitor_result_of_t = typename visitor_result_of< FnT, VariantTs... >::type

Functions
template<typename VariantT , typename... FnTs>
auto	match (VariantT &variant, FnTs &&...fns) -> estd::enable_if_t< detail::is_boost_variant< estd::decay_t< VariantT > >
	Destructure a boost::variant with a given set of functions. More...
template<typename VariantT , typename... FnTs>
auto	match (const VariantT &variant, FnTs &&...fns) -> estd::enable_if_t< detail::is_boost_variant< estd::decay_t< VariantT > >
template<typename VariantT , typename... FnTs>
auto	match (VariantT &&variant, FnTs &&...fns) -> estd::enable_if_t< detail::is_eggs_variant< estd::decay_t< VariantT > >
	Destructure a eggs::variant with a given set of functions. More...
	ABL_METAFUNCTION_T (variant_types)
template<typename ReturnType = void, typename Fn = detail::default_construct<ReturnType>>
otherwise_t< Fn, ReturnType >	otherwise (Fn &&fn=Fn())
template<typename... Args, typename Fn >
when_t< Fn, typename boost::mpl::if_< std::is_reference< Args >, Args, const Args & >::type... >	when (Fn &&fn)
	Factory for when functors. More...
template<typename... FnTs>
auto	visitor (FnTs &&...fns) -> visitor_t< meta::common_type_t< typename std::result_of< FnTs(meta::bottom)>::type... >, FnTs... >
	Returns a visitor object that can be used to deconstruct various variant types, created by composing the functions fns.... More...
template<typename FnT >
auto	visitor (FnT &&fn) -> FnT &&
template<typename VariantT , typename... FnTs>
auto	visitor_for (FnTs &&...fns) -> visitor_t< visitor_result_of_t< detail::visitor_impl< FnTs... >, variant_types_t< VariantT > >, FnTs... >
	Like visitor, but it uses the variant_types in VariantT to deduce what the return type of the visitor should be. More...
template<typename VarianT , typename FnT >
auto	visitor_for (FnT &&fn) -> FnT &&

Detailed Description

Tools for better usability of boost::variant, eggs::variant and potentially other implementations of sum types.

Function Documentation

auto atria::variant::match	(	VariantT &&	variant,
		FnTs &&...	fns
	)		-> estd::enable_if_t< detail::is_eggs_variant<estd::decay_t<VariantT> >

Destructure a eggs::variant with a given set of functions.

This uses C++ function overload rules to pick the right function. If the passed in variant is a non-const l-value, alternatives can destructure by reference and mutate the variant in place.

Note

This method can destructure either instances of eggs::variant<...> or for subclasses of eggs::variant<Ts...> for which meta::variant_types is defined to return meta::pack<Ts...>.

Returns

The return type is deduced as the meta::common_type<> of the result of destructuring all alternatives in the variant.

Definition at line 66 of file match_eggs.hpp.

auto atria::variant::match	(	VariantT &	variant,
		FnTs &&...	fns
	)		-> estd::enable_if_t< detail::is_boost_variant<estd::decay_t<VariantT> >

Destructure a boost::variant with a given set of functions.

This uses C++ function overload rules to pick the right function. If the passed in variant is a non-const l-value, alternatives can destructure by reference and mutate the variant in place.

Note

This method can destructure either instances of boost::variant<...> or for subclasses of boost::variant<Ts...> for which meta::variant_types is defined to return meta::pack<Ts...>.

boost::variant does not support destructuring by r-value reference, and so doesn't this.

Returns

The return type is deduced as the meta::common_type<> of the result of destructuring all alternatives in the variant.

Definition at line 69 of file match_boost.hpp.

auto atria::variant::visitor

(

FnTs &&...

fns

)

-> visitor_t< meta::common_type_t< typename std::result_of<FnTs(meta::bottom)>::type...>, FnTs...>

Returns a visitor object that can be used to deconstruct various variant types, created by composing the functions fns....

It attempts to deduce the return type of the function, but this might fail when generic functions are passed in.

Definition at line 253 of file visitor.hpp.

auto atria::variant::visitor_for

(

FnTs &&...

fns

)

-> visitor_t< visitor_result_of_t< detail::visitor_impl<FnTs...>, variant_types_t<VariantT> >, FnTs...>

Like visitor, but it uses the variant_types in VariantT to deduce what the return type of the visitor should be.

This allows it to deduce it even if generic functions are passed in.

Definition at line 274 of file visitor.hpp.

when_t<Fn, typename boost::mpl::if_<std::is_reference<Args>, Args, const Args&>::type...> atria::variant::when

(

Fn &&

fn

)

Factory for when functors.

Returns a wrapper for functor F with signature fixed to Args. Copy arguments are converted to const&, which eases use with std::bind and std::mem_fn.

Definition at line 191 of file visitor.hpp.