toDigit method
Implementation
@override
int toDigit(String ch) {
if (ch.codeUnitAt(0) >= '0'.codeUnitAt(0) &&
ch.codeUnitAt(0) <= '9'.codeUnitAt(0)) {
return ch.codeUnitAt(0) - 48;
}
if (ch.codeUnitAt(0) >= 'a'.codeUnitAt(0) &&
ch.codeUnitAt(0) <= 'z'.codeUnitAt(0)) {
return ch.codeUnitAt(0) - 97 + 10;
}
throw AssertionError('Not valid digit: ' + ch);
}