slices: add slices.Unique

Author: antonsacred

src/slices/slices.go

@@ -474,3 +474,15 @@ func Concat[S ~[]E, E any](slices ...S) S {
 	}
 	return newslice
 }
+
+// Unique replaces runs of equal elements with a single copy.
+// Unique modifies the contents of the slice s and returns the modified slice,
+// which may have a smaller length.
+func Unique[S ~[]E, E comparable](s S) S {
+	for i := len(s) - 1; i > 0; i-- {
+		if Index(s, s[i]) != i {
+			s = Delete(s, i, i+1)
+		}
+	}
+	return s
+}

src/slices/slices_test.go

@@ -1335,3 +1335,49 @@ func TestConcat_too_large(t *testing.T) {
 		}
 	}
 }
+
+var uniqueTests = []struct {
+	name string
+	s    []int
+	want []int
+}{
+	{
+		"nil",
+		nil,
+		nil,
+	},
+	{
+		"one",
+		[]int{1},
+		[]int{1},
+	},
+	{
+		"sorted",
+		[]int{1, 2, 3},
+		[]int{1, 2, 3},
+	},
+	{
+		"1 item",
+		[]int{1, 1, 2},
+		[]int{1, 2},
+	},
+	{
+		"unsorted",
+		[]int{1, 2, 1},
+		[]int{1, 2},
+	},
+	{
+		"many",
+		[]int{1, 2, 2, 3, 3, 4},
+		[]int{1, 2, 3, 4},
+	},
+}
+
+func TestUnique(t *testing.T) {
+	for _, test := range uniqueTests {
+		sliceCopy := Clone(test.s)
+		if got := Unique(sliceCopy); !Equal(got, test.want) {
+			t.Errorf("Unique(%v) = %v, want %v", test.s, got, test.want)
+		}
+	}
+}