[#boost-urls-grammar-is_charset]
= xref:boost.adoc[boost]::xref:boost/urls.adoc[urls]::xref:boost/urls/grammar.adoc[grammar]::is&lowbar;charset
:relfileprefix: ../../../
:mrdocs:

Alias for `std&colon;&colon;true&lowbar;type` if T satisfies xref:boost/urls/grammar/CharSet.adoc[`CharSet`]&period;

== Synopsis

Declared in `&lt;https://www.github.com/boostorg/url/blob/develop/include/boost/url/grammar/charset.hpp#L66[boost&sol;url&sol;grammar&sol;charset&period;hpp]&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template&lt;class T&gt;
using is&lowbar;charset = &sol;&ast; implementation-defined &ast;&sol;;
----

== Description

This metafunction determines if the type `T` meets these requirements of _CharSet_&colon;

* An instance of &grave;T&grave; is invocable    with this equivalent function signature&colon;

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

Use with `enable&lowbar;if` on the return value&colon;

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

[cols=2]
|===
| Name
| Description
| *T*
| the type to check&period;
|===


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