boost::urls::grammar::variant_rule

Match one of a set of rules

Synopsis

Declared in <include/boost/url/grammar/variant_rule.hpp>

template<
    Rule R0,
    Rule…​ Rn>
constexpr
/* implementation-defined */
variant_rule(
    R0 const& r0,
    Rn const&…​ rn) noexcept;

Description

Each specified rule is tried in sequence. When the first match occurs, the result is stored and returned in the variant. If no match occurs, an error is returned.

using value_type = variant< typename Rules::value_type... >;

Example

Rules are used with the function parse.

// request-target = origin-form
//                / absolute-form
//                / authority-form
//                / asterisk-form

system::result< variant< url_view, url_view, authority_view, core::string_view > > rv = grammar::parse(
    "/index.html?width=full",
    variant_rule(
        origin_form_rule,
        absolute_uri_rule,
        authority_rule,
        delim_rule('*') ) );
variant     = rule1 / rule2 / rule3...

See Also

absolute_uri_rule, authority_rule, delim_rule, parse, origin_form_rule, url_view.

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