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


Match a repeating number of elements

== Synopsis


Declared in `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/grammar/range_rule.hpp#L381[boost/url/grammar/range_rule.hpp]>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<xref:boost/urls/grammar/Rule.adoc[Rule] R>
constexpr
/* implementation-defined */::xref:boost/urls/grammar/implementation_defined/range_rule_t.adoc[range_rule_t]<R>
xref:boost/urls/grammar/range_rule-00.adoc[range_rule](
    R const& next,
    std::size_t N = 0,
    std::size_t M = std::size_t(‐1)) noexcept;
----

[.small]#xref:boost/urls/grammar/range_rule-00.adoc[_» more..._]#

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    xref:boost/urls/grammar/Rule.adoc[Rule] R1,
    xref:boost/urls/grammar/Rule.adoc[Rule] R2>
constexpr
/* implementation-defined */::xref:boost/urls/grammar/implementation_defined/range_rule_t.adoc[range_rule_t]<R1, R2>
xref:boost/urls/grammar/range_rule-06.adoc[range_rule](
    R1 const& first,
    R2 const& next,
    std::size_t N = 0,
    std::size_t M = std::size_t(‐1)) noexcept
requires ! std::is_integral<R2>::value;
----

[.small]#xref:boost/urls/grammar/range_rule-06.adoc[_» more..._]#

== Description


Elements are matched using the passed rule.        Normally when the rule returns an error,    the range ends and the input is rewound to    one past the last character that matched    successfully. However, if the rule returns    the special value xref:boost/urls/grammar/error.adoc[error::end_of_range], the    input is not rewound. This allows for rules    which consume input without producing    elements in the range. For example, to    relax the grammar for a comma‐delimited    list by allowing extra commas in between    elements.


=== Value Type

[,cpp]
----
using value_type = range< typename Rule::value_type >;
----

=== Example

Rules are used with the function xref:boost/urls/grammar/parse-02.adoc[parse]&period;

[,cpp]
----
// range    = 1*( ";" token )

system::result< range<core::string_view> > rv = parse( ";alpha;xray;charlie",
    range_rule(
        tuple_rule(
            squelch( delim_rule( ';' ) ),
            token_rule( alpha_chars ) ),
        1 ) );
----

=== BNF

[,cpp]
----
range        = <N>*<M>next
----

=== Specification

* link:https://datatracker.ietf.org/doc/html/rfc5234#section-3.6[3&period;6&period;  Variable Repetition (rfc5234)]



== Parameters


|===
| Name | Description

| *next*
| The rule to use for matching    each element&period; The range extends until this    rule returns an error&period;


| *N*
| The minimum number of elements for    the range to be valid&period; If omitted, this    defaults to zero&period;


| *M*
| The maximum number of elements for    the range to be valid&period; If omitted, this    defaults to unlimited&period;


| *first*
| The rule to use for matching    the first element&period; If this rule returns    an error, the range is empty&period;


|===

== See Also


xref:boost/urls/grammar/alpha_chars.adoc[alpha&lowbar;chars],        xref:boost/urls/grammar/delim_rule-01.adoc[delim&lowbar;rule],        xref:boost/urls/grammar/error.adoc[error&colon;&colon;end&lowbar;of&lowbar;range],        xref:boost/urls/grammar/parse-02.adoc[parse],        xref:boost/urls/grammar/range.adoc[range],        xref:boost/urls/grammar/tuple_rule.adoc[tuple&lowbar;rule],        xref:boost/urls/grammar/squelch.adoc[squelch]&period;






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