[#boost-urls-grammar-delim_rule-09]
= xref:boost.adoc[boost]::xref:boost/urls.adoc[urls]::xref:boost/urls/grammar.adoc[grammar]::delim&lowbar;rule
:relfileprefix: ../../../
:mrdocs:

Match a single character from a character set

== Synopsis

Declared in `&lt;https://www.github.com/boostorg/url/blob/develop/include/boost/url/grammar/delim_rule.hpp#L157[boost&sol;url&sol;grammar&sol;delim&lowbar;rule&period;hpp]&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template&lt;xref:boost/urls/grammar/CharSet.adoc[CharSet] CS&gt;
constexpr
&sol;&ast; implementation-defined &ast;&sol;
delim&lowbar;rule(CS const& cs) noexcept
requires ! std&colon;&colon;is&lowbar;convertible&lt;
        CS, char&gt;&colon;&colon;value;
----

== Description

This matches exactly one character which belongs to the specified character set&period; The value is a reference to the character in the underlying buffer, expressed as a `core&colon;&colon;string&lowbar;view`&period; The function xref:boost/urls/grammar/squelch.adoc[`squelch`] may be used to turn this into `void` instead&period; If there is no more input, the error code xref:boost/urls/grammar/error.adoc[`error&colon;&colon;need&lowbar;more`] is returned&period;

== Value Type
[,cpp]
----
using value_type = core::string_view;
----
== Example
Rules are used with the function xref:boost/urls/grammar/parse-09.adoc[`parse`]&period;

[,cpp]
----
system::result< core::string_view > rv = parse( "X", delim_rule( alpha_chars ) );
----
== Return Value

A rule which matches a single character from the set&period;

== Parameters

[cols=2]
|===
| Name
| Description
| *cs*
| The character set to use&period;
|===

== See Also

xref:boost/urls/grammar/alpha_chars.adoc[`alpha&lowbar;chars`], xref:boost/urls/grammar/parse-09.adoc[`parse`], xref:boost/urls/grammar/squelch.adoc[`squelch`]&period;


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