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#### query_rule

Rule for query.

##### Synopsis

Defined in header `<boost/url/rfc/query_rule.hpp>`

    constexpr implementation-defined query_rule;

##### Value Type

    using value_type = params_encoded_view;

##### Example

Rules are used with the function `grammar::parse`.

    system::result< params_encoded_view > rv = grammar::parse( "format=web&id=42&compact" , query_rule );

##### BNF

    query           = *( pchar / "/" / "?" )

    query-params    = [ query-param ] *( "&" query-param )
    query-param     = key [ "=" value ]
    key             = *qpchar
    value           = *( qpchar / "=" )
    qpchar          = unreserved
                    / pct-encoded
                    / "!" / "$" / "'" / "(" / ")"
                    / "*" / "+" / "," / ";"
                    / ":" / "@" / "/" / "?"

##### Specification

- 3.4. Query (rfc3986)

##### See Also

`grammar::parse`, `params_encoded_view`.

Convenience header `<boost/url.hpp>`