The reserved character set
<include/boost/url/rfc/reserved_chars.hpp>
constexpr
auto const reserved_chars = ~unreserved_chars;
the functions grammar::find_if and grammar::find_if_not .
system::result< decode_view > rv = grammar::parse( "Program%20Files", pct_encoded_rule( reserved_chars ) );
grammar::find_if , grammar::find_if_not , grammar::parse , pct_encoded_rule .