<boost/url/rfc/unreserved_chars.hpp>
constexpr grammar::lut_chars unreserved_chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz"
"0123456789"
"-._~";
Character sets are used with rules and the functions grammar::find_if
and grammar::find_if_not
.
system::result< decode_view > rv = grammar::parse( "Program%20Files", pct_encoded_rule( unreserved_chars ) );
unreserved = ALPHA / DIGIT / "-" / "." / "_" / "~"