rfc5646singleton top-level property

Rule rfc5646singleton
final

Implementation

final rfc5646singleton = rule(
  'singleton',
  alternatives([
    digit,
    valueRange(0x41, 0x57),
    valueRange(0x59, 0x5A),
    valueRange(0x61, 0x77),
    valueRange(0x79, 0x7A),
  ]),
);