add Min and Max functions

decimal.go

@@ -544,6 +544,40 @@ func (d *Decimal) ensureInitialized() {
 	}
 }
 
+// Returns the minimum Decimal that was passed in the arguments.
+//
+// To call this function with an array, you must do:
+//
+//     Min(arr[0], arr[1:]...)
+//
+// This makes it harder to accidentally call Min with 0 arguments.
+func Min(first Decimal, rest ...Decimal) Decimal {
+	ans := first
+	for _, item := range rest {
+		if item.Cmp(ans) < 0 {
+			ans = item
+		}
+	}
+	return ans
+}
+
+// Returns the maximum Decimal that was passed in the arguments.
+//
+// To call this function with an array, you must do:
+//
+//     Max(arr[0], arr[1:]...)
+//
+// This makes it harder to accidentally call Max with 0 arguments.
+func Max(first Decimal, rest ...Decimal) Decimal {
+	ans := first
+	for _, item := range rest {
+		if item.Cmp(ans) > 0 {
+			ans = item
+		}
+	}
+	return ans
+}
+
 func min(x, y int32) int32 {
 	if x >= y {
 		return y

decimal_test.go

@@ -711,6 +711,61 @@ func TestIntPart(t *testing.T) {
 	}
 }
 
+func TestDecimal_Min(t *testing.T) {
+	// the first element in the array is the expected answer, rest are inputs
+	testCases := [][]float64{
+		{0, 0},
+		{1, 1},
+		{-1, -1},
+		{1, 1, 2},
+		{-2, 1, 2, -2},
+		{-3, 0, 2, -2, -3},
+	}
+
+	for _, test := range testCases {
+		expected, input := test[0], test[1:]
+		expectedDecimal := NewFromFloat(expected)
+		decimalInput := []Decimal{}
+		for _, inp := range input {
+			d := NewFromFloat(inp)
+			decimalInput = append(decimalInput, d)
+		}
+		got := Min(decimalInput[0], decimalInput[1:]...)
+		if !got.Equals(expectedDecimal) {
+			t.Errorf("Expected %v, got %v, input=%+v", expectedDecimal, got,
+				decimalInput)
+		}
+	}
+}
+
+func TestDecimal_Max(t *testing.T) {
+	// the first element in the array is the expected answer, rest are inputs
+	testCases := [][]float64{
+		{0, 0},
+		{1, 1},
+		{-1, -1},
+		{2, 1, 2},
+		{2, 1, 2, -2},
+		{3, 0, 3, -2},
+		{-2, -3, -2},
+	}
+
+	for _, test := range testCases {
+		expected, input := test[0], test[1:]
+		expectedDecimal := NewFromFloat(expected)
+		decimalInput := []Decimal{}
+		for _, inp := range input {
+			d := NewFromFloat(inp)
+			decimalInput = append(decimalInput, d)
+		}
+		got := Max(decimalInput[0], decimalInput[1:]...)
+		if !got.Equals(expectedDecimal) {
+			t.Errorf("Expected %v, got %v, input=%+v", expectedDecimal, got,
+				decimalInput)
+		}
+	}
+}
+
 // old tests after this line
 
 func TestDecimal_Scale(t *testing.T) {