boost::urls::grammar::variant_rule

Match one of a set of rules

Synopsis

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

template<
    class R0,
    class... 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... >;

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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