Getting started with BrainFuck

Move value (aka pseudo-copy)

In order to move a value A to, say, next cell, we need to add 1 A times to the target (initially empty) cell.

It's like sum : we have A, 0 and we want 0, 0+A=A

Let's start

• Memory: A, 0
• Cursor: on A
• Input: any

Process

• while A is not null
  • invariant: A cell + next cell = A
  • decrease A
  • increase target
• loop
• A cell = 0, next cell = A - 0 = A

Code

[    while A is not null
  -  decrease A
  >+ increase target
  <  go back to A
]    loop

Minified version

[->+<]

Final state

• Memory: 0, A
• Cursor: "0" cell
• Input: unchanged
• Output: unchanged