Move (pseudo-copy) value

Context

To move (and not copy) a value A to another cell (here, next one), we need to add 1 A times to an empty cell and decrease A by 1 each time

Initial state

• Memory: A, 0
• Cursor: first cell
• Input: any

Process

• While first cell is not null, decrease first and increase second by 1, move back to first cell
• Loop invariant: sum of both cells is A
• When first cell equals 0, then second equals A

Code

[->+<]

Final state

• Memory: 0, A
• Cursor: first cell
• Input: any
• Output: unchanged