feat: adding WithoutNth (#575)

README.md

@@ -210,6 +210,7 @@ Supported intersection helpers:
 - [Union](#union)
 - [Without](#without)
 - [WithoutEmpty](#withoutempty)
+- [WithoutNth](#withoutnth)
 
 Supported search helpers:
 
@@ -2164,6 +2165,15 @@ subset := lo.WithoutEmpty([]int{0, 2, 10})
 // []int{2, 10}
 ```
 
+### WithoutNth
+
+Returns slice excluding nth value.
+
+```go
+subset := lo.WithoutNth([]int{-2, -1, 0, 1, 2}, 3, -42, 1)
+// []int{-2, 0, 2}
+```
+
 ### IndexOf
 
 Returns the index at which the first occurrence of a value is found in an array or return -1 if the value cannot be found.

intersect.go

@@ -167,9 +167,14 @@ func Union[T comparable, Slice ~[]T](lists ...Slice) Slice {
 
 // Without returns slice excluding all given values.
 func Without[T comparable, Slice ~[]T](collection Slice, exclude ...T) Slice {
+	excludeMap := make(map[T]struct{}, len(exclude))
+	for i := range exclude {
+		excludeMap[exclude[i]] = struct{}{}
+	}
+
 	result := make(Slice, 0, len(collection))
 	for i := range collection {
-		if !Contains(exclude, collection[i]) {
+		if _, ok := excludeMap[collection[i]]; !ok {
 			result = append(result, collection[i])
 		}
 	}
@@ -182,3 +187,24 @@ func Without[T comparable, Slice ~[]T](collection Slice, exclude ...T) Slice {
 func WithoutEmpty[T comparable, Slice ~[]T](collection Slice) Slice {
 	return Compact(collection)
 }
+
+// WithoutNth returns slice excluding nth value.
+func WithoutNth[T comparable, Slice ~[]T](collection Slice, nths ...int) Slice {
+	length := len(collection)
+
+	toRemove := make(map[int]struct{}, len(nths))
+	for i := range nths {
+		if nths[i] >= 0 && nths[i] <= length-1 {
+			toRemove[nths[i]] = struct{}{}
+		}
+	}
+
+	result := make(Slice, 0, len(collection))
+	for i := range collection {
+		if _, ok := toRemove[i]; !ok {
+			result = append(result, collection[i])
+		}
+	}
+
+	return result
+}

intersect_test.go

@@ -286,3 +286,25 @@ func TestWithoutEmpty(t *testing.T) {
 	nonempty := WithoutEmpty(allStrings)
 	is.IsType(nonempty, allStrings, "type preserved")
 }
+
+func TestWithoutNth(t *testing.T) {
+	t.Parallel()
+	is := assert.New(t)
+
+	result1 := WithoutNth([]int{5, 6, 7}, 1, 0)
+	is.Equal([]int{7}, result1)
+
+	result2 := WithoutNth([]int{1, 2})
+	is.Equal([]int{1, 2}, result2)
+
+	result3 := WithoutNth([]int{})
+	is.Equal([]int{}, result3)
+
+	result4 := WithoutNth([]int{0, 1, 2, 3}, -1, 4)
+	is.Equal([]int{0, 1, 2, 3}, result4)
+
+	type myStrings []string
+	allStrings := myStrings{"", "foo", "bar"}
+	nonempty := WithoutNth(allStrings)
+	is.IsType(nonempty, allStrings, "type preserved")
+}