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


The set of hexadecimal digits

== Synopsis


Declared in `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/grammar/hexdig_chars.hpp#L136[boost/url/grammar/hexdig_chars.hpp]>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
constexpr /* implementation-defined */::xref:boost/urls/grammar/implementation_defined/hexdig_chars_t.adoc[hexdig_chars_t] hexdig_chars = {};
----

== Description



=== Example

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 > rv = parse( "8086FC19", token_rule( hexdig_chars ) );
----

=== BNF

[,cpp]
----
HEXDIG      = DIGIT
            / "A" / "B" / "C" / "D" / "E" / "F"
            / "a" / "b" / "c" / "d" / "e" / "f"
----
[NOTE]
The RFCs are inconsistent on the case    sensitivity of hexadecimal digits&period; Existing    uses suggest case&hyphen;insensitivity is a de&hyphen;facto    standard&period;


=== Specification

* link:https://datatracker.ietf.org/doc/html/rfc5234#appendix-B.1[B&period;1&period; Core Rules (rfc5234)]
    
* link:https://datatracker.ietf.org/doc/html/rfc7230#section-1.2[1&period;2&period; Syntax Notation (rfc7230)]
    
* link:https://datatracker.ietf.org/doc/html/rfc5952#section-2.3[2&period;3&period; Uppercase or Lowercase (rfc5952)]
    
* link:https://datatracker.ietf.org/doc/html/rfc5952#section-4.3[4&period;3&period; Lowercase (rfc5952)]



== See Also


xref:boost/urls/grammar/find_if.adoc[find&lowbar;if],        xref:boost/urls/grammar/find_if_not.adoc[find&lowbar;if&lowbar;not],        xref:boost/urls/grammar/hexdig_value.adoc[hexdig&lowbar;value],        xref:boost/urls/grammar/parse-02.adoc[parse],        xref:boost/urls/grammar/token_rule.adoc[token&lowbar;rule]&period;






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