A wrapper to help with overload resolution for functions operating on an any. More...

#include <placeholder_of.hpp>

Public Types
typedef void	_boost_type_erasure_is_any
	INTERNAL ONLY. More...

typedef param	_boost_type_erasure_derived_type
	INTERNAL ONLY. More...

Public Member Functions
template<class U >
	param (any< Concept, U > &a, typename boost::enable_if< ::boost::type_erasure::detail::placeholder_conversion< U, T > >::type *=0)

template<class U >
	param (const any< Concept, U > &a, typename boost::enable_if< ::boost::type_erasure::detail::placeholder_conversion< typename::boost::add_const< U >::type, T > >::type *=0)

template<class U >
	param (any< Concept, U > &&a, typename boost::enable_if< ::boost::type_erasure::detail::placeholder_conversion< U &&, T > >::type *=0)

any< Concept, T >	get () const
	Returns the stored any. More...

Friends
struct	boost::type_erasure::detail::access

Detailed Description

template<class Concept, class T>
singleton boost::type_erasure::param< Concept, T >

A wrapper to help with overload resolution for functions operating on an any.

The template arguments are interpreted in the same way as any.

A parameter of type param can be initialized with an any that has the same Concept and base placeholder when there exists a corresponding standard conversion for the placeholder. A conversion sequence from any<C, P> to param<C, P1> is a better conversion sequence than any<C, P> to param<C, P2> iff the corresponding placeholder standard conversion sequence from P to P1 is a better conversion sequence than P to P2.

Note: Overloading based on cv-qualifiers and rvalue-ness is only supported in C++11. In C++03, all conversion sequences from any to param have the same rank.

Example:

void f(param<C, _a&>);
void f(param<C, const _a&>);
void g(param<C, const _a&>);
void g(param<C, _a&&>);
any<C, _a> a;
f(any<C, _a>()); // calls void f(param<C, const _a&>);
f(a);            // calls void f(param<C, _a&>); (ambiguous in C++03)
g(any<C, _a>()); // calls void g(param<C, _a&&>); (ambiguous in C++03)
g(a);            // calls void g(param<C, const _a&>);