format static method

String format(double value, { int decimals = 1, })

Formats value with up to decimals fractional digits, trimming trailing zeros. Handles NaN / infinity gracefully.

Implementation

static String format(double value, {int decimals = 1}) {
  if (value.isNaN) return 'NaN';
  if (value.isInfinite) return value > 0 ? '∞' : '-∞';

  final negative = value < 0;
  final magnitude = value.abs();
  var scale = 1;
  for (var i = 0; i < math.max(0, decimals); i++) {
    scale *= 10;
  }

  final scaled = (magnitude * scale).roundToDouble();
  final whole = scaled ~/ scale;
  final fracInt = (scaled.toInt()) % scale;

  if (fracInt == 0 || decimals <= 0) {
    return '${negative && (whole != 0 || scaled != 0) ? '-' : ''}$whole';
  }

  // Build the fractional part, trimming trailing zeros.
  var digits = '$fracInt';
  while (digits.length < decimals) {
    digits = '0$digits';
  }
  while (digits.endsWith('0')) {
    digits = digits.substring(0, digits.length - 1);
  }
  if (digits.isEmpty) {
    return '${negative ? '-' : ''}$whole';
  }
  return '${negative ? '-' : ''}$whole.$digits';
}