2018.10.05[Dart] ひらがな – カタカナ変換

String hiraToKana(String str) {
  return str.replaceAllMapped(new RegExp("[ぁ-ゔ]"), (Match m) => String.fromCharCode(m.group(0).codeUnitAt(0) + 0x60));
}

String kanaToHira(String str) {
  return str.replaceAllMapped(new RegExp("[ァ-ヴ]"), (Match m) => String.fromCharCode(m.group(0).codeUnitAt(0) - 0x60));
}