:relfileprefix: ../../../
[#boost-urls-grammar-alnum_chars]

== xref:boost.adoc[pass:[boost]]::xref:boost/urls.adoc[pass:[urls]]::xref:boost/urls/grammar.adoc[pass:[grammar]]::alnum_chars


The set of letters and digits


=== Synopsis

Declared in header `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/grammar/alnum_chars.hpp#L118[boost/url/grammar/alnum_chars.hpp,window=blank_]>`

[source,cpp,subs="verbatim,macros,-callouts"]
----
constexpr
pass:q[_implementation-defined_] alnum_chars = {};
----

=== Description


=== Character sets are used with rules and the

functions
xref:boost/urls/grammar/find_if.adoc[find_if]
and
xref:boost/urls/grammar/find_if_not.adoc[find_if_not]
.
[,cpp]
----
system::result< core::string_view > = parse( "Johnny42", token_rule( alnumchars ) );
----
[,cpp]
----
ALNUM       = ALPHA / DIGIT

ALPHA       = %x41-5A / %x61-7A
            ; A-Z / a-z

DIGIT       = %x30-39
            ; 0-9
----

* link:https://datatracker.ietf.org/doc/html/rfc5234#appendix-B.1[B.1. Core Rules (rfc5234)]



=== See Also


xref:boost/urls/grammar/find_if.adoc[find_if]
,
xref:boost/urls/grammar/find_if_not.adoc[find_if_not]
,
xref:boost/urls/grammar/parse-02.adoc[parse]
,
xref:boost/urls/grammar/token_rule.adoc[token_rule]
.