Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

This is the documentation for an old version of Boost. Click here to view this page for the latest version.

grammar::squelch

Squelch the value of a rule.

Synopsis

Defined in header <boost/url/grammar/tuple_rule.hpp>

template<
    class Rule>
constexpr implementation-defined
squelch(
    Rule const& r);

Description

This function returns a new rule which matches the specified rule, and converts its value type to void. This is useful for matching delimiters in a grammar, where the value for the delimiter is not needed.

Value Type

using value_type = void;

Example 1

With squelch:

result< std::tuple< decode_view, string_view > > rv = parse(
    "www.example.com:443",
    tuple_rule(
        pct_encoded_rule(unreserved_chars + '-' + '.'),
        squelch( delim_rule( ':' ) ),
        token_rule( digit_chars ) ) );

Example 2

Without squelch:

result< std::tuple< decode_view, string_view, string_view > > rv = parse(
    "www.example.com:443",
    tuple_rule(
        pct_encoded_rule(unreserved_chars + '-' + '.'),
        delim_rule( ':' ),
        token_rule( digit_chars ) ) );

Parameters

Name	Description
`r`	The rule to squelch

See Also

delim_rule, digit_chars, parse, tuple_rule, token_rule, decode_view, pct_encoded_rule, unreserved_chars.

Convenience header <boost/url/grammar.hpp>