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DPAmar
4,418 views

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
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