Created
September 26, 2020 20:10
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Play with the Collatz conjecture in Formality
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| Collatz.run: IO(Unit) | |
| do IO { | |
| var val_str = IO.prompt("start value:"); | |
| let start = Nat.parse_decimal(val_str); | |
| Collatz.step(start); | |
| } | |
| Collatz.step(start: Nat): IO(Unit) | |
| let next = Collatz.next(start); | |
| do IO { | |
| IO.print(Nat.show(next)); | |
| case Nat.eql(next, 1): | |
| | Bool.true => IO.print("Loop found!"); | |
| | Bool.false => Collatz.step(next);; | |
| } | |
| Collatz.next(start: Nat): Nat | |
| if Nat.odd(start) then | |
| Nat.add(Nat.mul(3, start), 1) | |
| else | |
| Nat.div(start, 2) |
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