- comparator with tests

utils/comparator.go

@@ -0,0 +1,40 @@
+package utils
+
+// Comparator will make type assertion (see IntComparator for example),
+// which will panic if a or b are not of the asserted type.
+//
+// Should return:
+//   -1, if a < b
+//    0, if a == b
+//    1, if a > b
+type Comparator func(a, b interface{}) int
+
+func IntComparator(a, b interface{}) int {
+	aInt := a.(int)
+	bInt := b.(int)
+	switch {
+	case aInt > bInt:
+		return 1
+	case aInt < bInt:
+		return -1
+	default:
+		return 0
+	}
+}
+
+func StringComparator(a, b interface{}) int {
+	s1 := a.(string)
+	s2 := b.(string)
+	min := len(s2)
+	if len(s1) < len(s2) {
+		min = len(s1)
+	}
+	diff := 0
+	for i := 0; i < min && diff == 0; i++ {
+		diff = int(s1[i]) - int(s2[i])
+	}
+	if diff == 0 {
+		diff = len(s1) - len(s2)
+	}
+	return diff
+}

utils/comparator_test.go

@@ -0,0 +1,45 @@
+package utils
+
+import "testing"
+
+func TestIntComparator(t *testing.T) {
+
+	tests := [][]interface{}{
+		{1, 1, 0},
+		{1, 2, -1},
+		{2, 1, 1},
+		{11, 22, -1},
+		{0, 0, 0},
+		{1, 0, 1},
+		{0, 1, -1},
+	}
+
+	for _, test := range tests {
+		actual := IntComparator(test[0], test[1])
+		expected := test[2]
+		if actual != expected {
+			t.Errorf("Got %v expected %v", actual, expected)
+		}
+	}
+}
+
+func TestStringComparator(t *testing.T) {
+
+	tests := [][]interface{}{
+		{"a", "a", 0},
+		{"a", "b", -1},
+		{"b", "a", 1},
+		{"aa", "aab", -1},
+		{"", "", 0},
+		{"a", "", 1},
+		{"", "a", -1},
+	}
+
+	for _, test := range tests {
+		actual := StringComparator(test[0], test[1])
+		expected := test[2]
+		if actual != expected {
+			t.Errorf("Got %v expected %v", actual, expected)
+		}
+	}
+}