Function TestDecimal_DivRound

decimal_test.go:2064–2101

rules for rounded divide, rounded to integer rounded_divide(d,d2) = q sign q * sign (d/d2) >= 0 for d and d2 >0 : q is already rounded q = d/d2 + r , with r > -0.5 and r <= 0.5 thus q-d/d2 = r, with r > -0.5 and r <= 0.5 and d2 q -d = r d2 with r d2 > -d2/2 and r d2 <= d2/2 and 2 (d2 q -d) = x with

(t *testing.T)

// if we factor in precision then x > -d2 * 10^(-precision) and x <= d2 * 10(-precision)

func TestDecimal_DivRound(t *testing.T) {
	cases := []struct {
		d      string
		d2     string
		prec   int32
		result string
	}{
		{"2", "2", 0, "1"},
		{"1", "2", 0, "1"},
		{"-1", "2", 0, "-1"},
		{"-1", "-2", 0, "1"},
		{"1", "-2", 0, "-1"},
		{"1", "-20", 1, "-0.1"},
		{"1", "-20", 2, "-0.05"},
		{"1", "20.0000000000000000001", 1, "0"},
		{"1", "19.9999999999999999999", 1, "0.1"},
	}
	for _, s := range cases {
		d, _ := NewFromString(s.d)
		d2, _ := NewFromString(s.d2)
		result, _ := NewFromString(s.result)
		prec := s.prec
		q := d.DivRound(d2, prec)
		if sign(q)*sign(d)*sign(d2) < 0 {
			t.Errorf("sign of quotient wrong, got: %v/%v is about %v", d, d2, q)
		}
		x := q.Mul(d2).Abs().Sub(d.Abs()).Mul(New(2, 0))
		if x.Cmp(d2.Abs().Mul(New(1, -prec))) > 0 {
			t.Errorf("wrong rounding, got: %v/%v prec=%d is about %v", d, d2, prec, q)
		}
		if x.Cmp(d2.Abs().Mul(New(-1, -prec))) <= 0 {
			t.Errorf("wrong rounding, got: %v/%v prec=%d is about %v", d, d2, prec, q)
		}
		if !q.Equal(result) {
			t.Errorf("rounded division wrong %s / %s scale %d = %s, got %v", s.d, s.d2, prec, s.result, q)
		}
	}
}

func TestDecimal_DivRound2(t *testing.T) {
	for _, tc := range createDivTestCases() {