OP_ROLL

INFO

Opcode number: 122
Byte representation: 0x7a
Short description: Move the stack item at position n to the top of the stack.

OP_ROLL is used to select a stack item and move it to the top.

Notes

• If there are fewer than two items on the stack, if n is negative, or if n is larger than the stack when OP_ROLL is executed, the script will fail.
• The stack item just before OP_ROLL dictates 'n', the location of the item to be moved.
• Counting begins at 0, not 1; so an n value of 2 would reach the third stack item (0 is first, 1 is second, 2 is third, and so on).

Examples

Example 1

Moving the nth stack item when n==2 with five total items (i.e., the third item from the top moves to the top):

# ASM script
OP_1 OP_2 OP_3 OP_4 OP_5 OP_2 OP_ROLL

# Raw script
5152535455527a

# Stack (before OP_ROLL)
2
5
4
3
2
1

# Stack (after OP_ROLL)
3
5
4
2
1

Example 2

Moving the nth stack item when n==3 with four total items (i.e., the fourth item from the top moves to the top):

# ASM script
OP_7 OP_8 OP_9 OP_10 OP_3 OP_ROLL

# Raw script
5758595a537a

# Stack (before OP_ROLL)
3
10
9
8
7

# Stack (after OP_ROLL)
7
10
9
8