Add Sign method

d.Sign() is a more convenient way of saying d.Cmp(Zero).

decimal.go

@@ -411,6 +411,19 @@ func (d Decimal) Equals(d2 Decimal) bool {
 	return d.Equal(d2)
 }
 
+// Sign returns:
+//
+//	-1 if d <  0
+//	 0 if d == 0
+//	+1 if d >  0
+//
+func (d Decimal) Sign() int {
+	if d.value == nil {
+		return 0
+	}
+	return d.value.Sign()
+}
+
 // Exponent returns the exponent, or scale component of the decimal.
 func (d Decimal) Exponent() int32 {
 	return d.exp

decimal_test.go

@@ -506,6 +506,9 @@ func TestDecimal_Uninitialized(t *testing.T) {
 	if a.Cmp(b) != 0 {
 		t.Errorf("a != b")
 	}
+	if a.Sign() != 0 {
+		t.Errorf("a.Sign() != 0")
+	}
 	if a.Exponent() != 0 {
 		t.Errorf("a.Exponent() != 0")
 	}
@@ -1292,6 +1295,22 @@ func TestPow(t *testing.T) {
 	}
 }
 
+func TestDecimal_Sign(t *testing.T) {
+	if Zero.Sign() != 0 {
+		t.Errorf("%q should have sign 0", Zero)
+	}
+
+	one := New(1, 0)
+	if one.Sign() != 1 {
+		t.Errorf("%q should have sign 1", one)
+	}
+
+	mone := New(-1, 0)
+	if mone.Sign() != -1 {
+		t.Errorf("%q should have sign -1", mone)
+	}
+}
+
 func didPanic(f func()) bool {
 	ret := false
 	func() {