roll

Input Stack: n: Int ...

⇨

Output Stack: item: Any ...

Move an item from a specific position in the stack to the top. Unlike :pick which copies an item, :roll removes the item from its original position and places it on top. This is useful for reorganizing the stack when you need to bring buried items to the surface.

Parameters

• ...: The current stack contents with at least (n+1) items
• n: Zero-based index of the item to move (0 = top item, 1 = second item, etc.)

Examples

Rolling the top item (index 0) - effectively a no-op:

a,0,:roll

Pos	Input	Output
0	0	a
1	a

Rolling the top item from a two-item stack:

a,b,0,:roll

Pos	Input	Output
0	0	b
1	b	a
2	a

Rolling the second item (index 1) to the top:

a,b,1,:roll

Pos	Input	Output
0	1	a
1	b	b
2	a

Difference from Pick

Operation	Effect	Stack Size Change
:pick	Copy item to top	+1 (grows)
:roll	Move item to top	0 (unchanged)

Related Operations

• :pick - Copy (not move) item to top of stack
• :rot / :-rot - Rotate top three items
• :swap - Exchange top two items (equivalent to 1,:roll)
• :depth - Check stack size before rolling
• :over - Copy second item (non-destructive alternative)

Since: 1.5.0