{12999999, 4, "12990000", "13000000", "13000000"},
	} {
		x := nat(nil).setUint64(test.x)

		var d decimal
		d.init(x, 0)
		d.roundDown(test.n)
		if got := d.String(); got != test.down {
			t.Errorf("roundDown(%d, %d) = %s; want %s", test.x, test.n, got, test.down)
		}

		d.init(x, 0)
		d.round(test.n)
		if got := d.String(); got != test.even {

}

func TestDecimalRound(t *testing.T) {
	for i := 0; i < len(roundtests); i++ {
		test := &roundtests[i]
		d := NewDecimal(test.i)
		d.RoundDown(test.nd)
		s := d.String()
		if s != test.down {
			t.Errorf("Decimal %v RoundDown %d = %v, want %v",
				test.i, test.nd, s, test.down)
		}
		d = NewDecimal(test.i)
		d.Round(test.nd)
		s = d.String()
		if s != test.round {

// If n < 0, x remains unchanged.
func (x *decimal) round(n int) {
	if n < 0 || n >= len(x.mant) {
		return // nothing to do
	}

	if shouldRoundUp(x, n) {
		x.roundUp(n)
	} else {
		x.roundDown(n)
	}
}

func (x *decimal) roundUp(n int) {
	if n < 0 || n >= len(x.mant) {
		return // nothing to do
	}
	// 0 <= n < len(x.mant)

	// find first digit < '9'