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Enable retrieval of element in array/slice which is neither head nor tail. #163

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25 changes: 24 additions & 1 deletion scan.go
Original file line number Diff line number Diff line change
Expand Up @@ -164,6 +164,29 @@ func Last(arr interface{}) interface{} {
panic(fmt.Sprintf("Type %s is not supported by Last", valueType.String()))
}

// ElementAt gets the element of array at the given index.
func ElementAt(arr interface{}, index int) interface{} {
value := redirectValue(reflect.ValueOf(arr))
valueType := value.Type()

kind := value.Kind()

if kind == reflect.Array || kind == reflect.Slice {
if value.Len() == 0 {
return nil
}

if index < 0 || index >= value.Len() {
// maybe panic?
return nil
}

return value.Index(index).Interface()
}

panic(fmt.Sprintf("Type %s is not supported by ElementAt", valueType.String()))
}

// Initial gets all but the last element of array.
func Initial(arr interface{}) interface{} {
value := redirectValue(reflect.ValueOf(arr))
Expand Down Expand Up @@ -201,5 +224,5 @@ func Tail(arr interface{}) interface{} {
return value.Slice(1, length).Interface()
}

panic(fmt.Sprintf("Type %s is not supported by Initial", valueType.String()))
panic(fmt.Sprintf("Type %s is not supported by Tail", valueType.String()))
}
15 changes: 15 additions & 0 deletions scan_test.go
Original file line number Diff line number Diff line change
Expand Up @@ -103,6 +103,21 @@ func TestLast(t *testing.T) {
is.Equal(Last([]int{1, 2, 3, 4}), 4)
}

func TestElementAt(t *testing.T) {
is := assert.New(t)

for k, v := range map[int]interface{}{
-1: nil,
0: 1,
1: 2,
2: 3,
3: 4,
5: nil,
} {
is.Equal(ElementAt([]int{1, 2, 3, 4}, k), v)
}
}

func TestTail(t *testing.T) {
is := assert.New(t)

Expand Down