[#boost-urls-grammar-is_charset]
= xref:boost.adoc[boost]::xref:boost/urls.adoc[urls]::xref:boost/urls/grammar.adoc[grammar]::is_charset
:relfileprefix: ../../../
:mrdocs:


Alias for `std::true_type` if T satisfies xref:boost/urls/grammar/CharSet.adoc[CharSet].

== Synopsis


Declared in `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/grammar/charset.hpp#L66[boost/url/grammar/charset.hpp]>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<class T>
using is_charset = /* implementation-defined */::xref:boost/urls/grammar/implementation_defined/is_charset.adoc[is_charset]<T>;
----

== Description


This metafunction determines if the    type `T` meets these requirements of    _CharSet_:

* An instance of 
`T`
 is invocable    with this equivalent function signature:
    

[,cpp]
----
bool T::operator()( char ) const noexcept;
----

=== Example

Use with `enable_if` on the return value:

[,cpp]
----
template< class CharSet >
typename std::enable_if< is_charset<T>::value >::type
func( CharSet const& cs );
----


== Template Parameters


|===
| Name | Description

| *T*
| the type to check&period;


|===



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