---
title: roList
slug: develop/rolist
docTags: 
createdAt: 2025-03-11T07:07:17.200Z
---

This object functions as a general-purpose, doubly linked list. It can be used as a container for arbitrary-length lists of BrightSign objects. The array operator \[ ] can be used to access any element in an ordered list. 

## ifList

### Count() As Integer

Returns the number of elements in the list.

### ResetIndex() As Boolean

Resets the current index or position in the list to the head element.

### AddTail(obj As Object) As Void

Adds a typed value to the tail of the list.

### AddHead(obj As Object) As Void

Adds a typed value to the head of the list.

### RemoveIndex() As Object

Removes an entry from the list at the current index or position and increments the index or position in the list. It returns `Invalid` when the end of the list is reached.

### GetIndex() As Object

Retrieves an entry from the list at the current index or position and increments the index or position in the list. It returns `Invalid` when the end of the list is reached.

### RemoveTail() As Object

Removes the entry at the tail of the list.

### RemoveHead() As Object

Removes the entry at the head of the list.

### GetTail() As Object

Retrieves the entry at the tail of the list and keeps the entry in the list.

### GetHead() As Object

Retrieves the entry at the head of the list and keeps the entry in the list.

### Clear()

Removes all elements from the list.

## ifEnum

### Reset()

Resets the position to the first element of enumeration.

### Next() As Dynamic

Returns a typed value at the current position and increment position.

### IsNext() As Boolean

Returns `True` if there is a next element.

### IsEmpty() As Boolean

Returns `True` if there is not an exact statement.

## ifArray

### Peek() As Dynamic

Returns the last (highest index) list entry without removing it.

### Pop() As Dynamic

Returns the last (highest index) entry and removes it from the list.

### Push(entry As Dynamic)

Adds a new highest-index entry to the end of the list.

### Shift() As Dynamic

Removes index zero from the list and shifts all other entries down by one unit.

### Unshift(entry As Dynamic)

Adds a new index zero to the list and shifts all other entries up by one unit.

### Delete(index As Integer) As Boolean

Deletes the indicated list entry and shifts all above entries down by one unit.

### Count() As Integer

Returns the length of the list (i.e. the index of the highest entry in the list plus one).

### Clear()

Deletes every entry in the list.

### Append(list As roList)

Appends one *roList* to another. If the passed *roList* contains entries that were never set to a value, they are not appended.

:::hint{type="info"}
The two appended objects must be of the same type.
:::

## ifArrayGet 

### GetEntry(a As Integer) As Dynamic

Returns a list entry of a given index. Entries start at zero. If an entry that has not been set is fetched, Invalid is returned.

## ifArraySet

### SetEntry(a As Integer, b As Dynamic)

Sets an entry of a given index to the passed type value.

## Example

```text
list = CreateObject("roList")
list.AddTail("a")
list.AddTail("b")
list.AddTail("c")
list.AddTail("d") 
list.ResetIndex()
x= list.GetIndex()
while x <> invalid
print x
x = list.GetIndex()
end while 
print list[2]
```