}
		return fmtF(dst, neg, digs, max(prec-digs.dp, 0))
	}

	// unknown format
	return append(dst, '%', fmt)
}

// roundShortest rounds d (= mant * 2^exp) to the shortest number of digits
// that will let the original floating point value be precisely reconstructed.
func roundShortest(d *decimal, mant uint64, exp int, flt *floatInfo) {
	// If mantissa is zero, the number is zero; stop now.
	if mant == 0 {
		d.nd = 0

	var d decimal // == 0.0
	if x.form == finite {
		// x != 0
		d.init(x.mant, int(x.exp)-x.mant.bitLen())
	}

	// 2) round to desired precision
	shortest := false
	if prec < 0 {
		shortest = true
		roundShortest(&d, x)
		// Precision for shortest representation mode.
		switch fmt {
		case 'e', 'E':
			prec = len(d.mant) - 1
		case 'f':
			prec = max(len(d.mant)-d.exp, 0)
		case 'g', 'G':
			prec = len(d.mant)