Decimal.parse constructor

Decimal.parse(String source)

Parses finite decimal text, including scientific notation.

Invalid syntax throws FormatException; unsupported magnitude or scale throws RangeError. No intermediate floating-point value is used.

Implementation

factory Decimal.parse(String source) {
  // Bound parsing work before allocating a potentially enormous BigInt.
  if (source.length > maxIntegerDigits + maxFractionDigits + 32) {
    throw const FormatException('Decimal input is too long.');
  }
  final match = _syntax.firstMatch(source);
  if (match == null ||
      match.end != source.length ||
      (match[2]!.isEmpty && (match[3] ?? '').isEmpty)) {
    throw const FormatException('Expected a finite decimal string.');
  }
  final exponent = int.tryParse(match[4] ?? '0');
  if (exponent == null ||
      exponent < -maxIntegerDigits - maxFractionDigits ||
      exponent > maxIntegerDigits + maxFractionDigits) {
    throw const FormatException('Decimal exponent is out of range.');
  }
  final fraction = match[3] ?? '';
  return Decimal._digits(
    '${match[2]}$fraction',
    match[1] == '-',
    fraction.length - exponent,
  );
}