adding slices.Insert

Author: zostay

Changes.md

@@ -1,3 +1,7 @@
+WIP  TBD
+
+ * Adding slices.Insert
+
 v0.5.0  2023-07-25
 
  * Adding fs.CreateFS, fs.WriteFileFS, fs.ReaderFS, fs.ReaderWriterFS, and fs.WriterFS

README.md

@@ -61,6 +61,9 @@ off-by-one errors, so the following ops are provided:
 
  * `FromRange(a, z, delta)`
  * `Delete(slice, index)`
+ * `DeleteValue(slice, value)`
+ * `DeleteAllValues(slice, value)`
+ * `Insert(slice, index, value)`
  * `Push(slice, value)`
  * `Pop(slice)`
  * `Shift(slice)`

slices/manipulate.go

@@ -1,5 +1,7 @@
 package slices
 
+import "github.com/zostay/go-std/generic"
+
 // Delete will remove the data at index i from the given slice. This works by
 // copying the data after it back and then shortening the slice by one element.
 func Delete[T any](slice []T, i int) []T {
@@ -33,6 +35,18 @@ func DeleteAllValues[T comparable](slice []T, s T) []T {
 	return slice
 }
 
+// Insert will add the data at index i into the given slice and shift the rest
+// of the data up one index.
+func Insert[T any](slice []T, i int, data T) []T {
+	if i == len(slice) {
+		return append(slice, data)
+	}
+	slice = append(slice, generic.Zero[T]())
+	copy(slice[i+1:], slice[i:])
+	slice[i] = data
+	return slice
+}
+
 // Push will add the given values to the end of the slice and return the newly
 // transformed slice. The slice must be allocated or this function will panic.
 func Push[T any](slice []T, v ...T) []T {

slices/manipulate_test.go

@@ -102,6 +102,24 @@ func TestDeleteAllValues(t *testing.T) {
 	})
 }
 
+func TestInsert(t *testing.T) {
+	s := []int{1, 2, 3}
+
+	s = slices.Insert(s, 0, 4)
+	s = slices.Insert(s, 2, 5)
+	s = slices.Insert(s, 5, 6)
+
+	assert.Equal(t, []int{4, 1, 5, 2, 3, 6}, s)
+
+	assert.Panics(t, func() {
+		s = slices.Insert(s, -1, 0)
+	})
+
+	assert.Panics(t, func() {
+		s = slices.Insert(s, 8, 7)
+	})
+}
+
 func TestPop(t *testing.T) {
 	s := []int{1, 2, 3}