adjustForExponent method

@override String adjustForExponent(String str)

Move the decimal point.

Implementation

@override
String adjustForExponent(String str) {
  if (str.isNotEmpty != true) return str;
  var trimmed = str.trim();
  var sign = '';
  if (trimmed.startsWith('-')) {
    sign = '-';
    trimmed = trimmed.substring(1);
  } else if (trimmed.startsWith('+')) {
    trimmed = trimmed.substring(1);
  }

  final dotIndex = trimmed.indexOf('.');
  final eIndex = trimmed.toLowerCase().indexOf('e');

  var firstNonZeroDigit = -1;
  for (var i = 0; i < trimmed.length; i++) {
    final s = trimmed[i];
    if (s != '0' && s != '.' && s != '-' && s != '+') {
      firstNonZeroDigit = i;
      break;
    }
  }

  if (firstNonZeroDigit == -1) return '0.0';

  final includedExponent =
      eIndex != -1 ? num.parse(trimmed.substring(eIndex + 1)) : 0;

  final length = eIndex != -1 ? eIndex : trimmed.length;
  var exp = (dotIndex == -1 ? length - 1 : dotIndex - firstNonZeroDigit) +
      includedExponent;
  if (dotIndex > firstNonZeroDigit) exp--;

  final num effExp = exp < 0 ? ((exp + 1) ~/ 3) * 3 - 3 : (exp ~/ 3) * 3;
  final adj = (exp - effExp).floor();

  var engStr = eIndex != -1
      ? trimmed.substring(firstNonZeroDigit, eIndex)
      : trimmed.substring(firstNonZeroDigit);
  if (engStr.length == 1 && firstNonZeroDigit < dotIndex) {
    engStr = '$engStr.0';
  } else {
    // Insert the decimal point after the first non zero digit.
    engStr = engStr.replaceAll('.', '');
    if (engStr.length < adj + 1) engStr = engStr.padRight(adj + 1, '0');
    engStr = '${engStr.substring(0, adj + 1)}.${engStr.substring(adj + 1)}';
    if (engStr.endsWith('.')) engStr = '${engStr}0';
  }

  engStr = NumberFormatSI.removeInsignificantZeros(engStr);

  // Prepend the sign.
  engStr = '$sign$engStr';

  // Append the exponent.
  if (effExp != 0) {
    engStr = unicode
        ? '$engStr \u{00d7} 10${unicodeExponent(effExp)}'
        : '$engStr x 10^$effExp';
  }

  return engStr;
}