swap

Input Stack: top: Any second: Any

⇨

Output Stack: second: Any top: Any

Exchange the positions of the top two items on the stack. This is one of the most commonly used stack manipulation operations, often needed when operands are in the wrong order for a binary operation.

Parameters

• top: The item currently at the top of the stack
• second: The item in the second position that will move to the top

Examples

Basic swap operation:

a,b,:swap

Pos	Input	Output
0	b	a
1	a	b

Common use case - getting operands in the correct order for division:

name,errors,:eq,
:sum,
name,requests,:eq,
:sum,
:swap,
:div

Related Operations

• :over - Copy the second item to the top
• :dup - Duplicate the top item
• :rot - Rotate three items (bottom to top)
• :-rot - Rotate three items (top to bottom)