function format(_ref) {
    var _ref2 = _slicedToArray(_ref, 3);

    var negative = _ref2[0];
    var intPart = _ref2[1];
    var fracPart = _ref2[2];

    if (intPart.length === 0) {
      intPart = '0';
    } else {
      var firstNonZeroIndex = undefined;
      for (firstNonZeroIndex = 0; firstNonZeroIndex < intPart.length; firstNonZeroIndex++) {
        if (intPart[firstNonZeroIndex] !== '0') {
          break;
        }
      }

      if (firstNonZeroIndex !== intPart.length) {
        intPart = intPart.slice(firstNonZeroIndex);
      }
    }

    return (negative ? NEG + intPart : intPart) + (fracPart.length ? SEP + fracPart : '');
  }
Format the given number configuration as a number string.

@example

  stround.format([false, '12', '34']); // '12.34'
  stround.format([true, '8', '']);     // '-8'
  stround.format([true, '', '7']);     // '-0.7'

@param {Array} parts
@return {string}