Interesting article. For those not familiar with the problem, it's called the Collatz conjecture.
I'm curious how this would behave in case of the conjecture being false, i.e. found a number that wouldn't reduce to 1 by the algorithm.
I'm curious how this would behave in case of the conjecture being false, i.e. found a number that wouldn't reduce to 1 by the algorithm.
The conjecture is also known as the 3n + 1 conjecture, the Ulam conjecture (after Stanisław Ulam), Kakutani's problem (after Shizuo Kakutani), the Thwaites conjecture (after Sir Bryan Thwaites), Hasse's algorithm (after Helmut Hasse), or the Syracuse problem; the sequence of numbers involved is referred to as the hailstone sequence or hailstone numbers,or as wondrous numbers.
I'm sure you could use contracts to prevent the latter and reasonably sure there's some option somewhere to set maximum recursion depth to prevent the prior.
EDIT: as opposed to boring method of just putting/checking a loop count accumulator and if not bignum? into the function body.
Of course, if you run it and get a stack overflow, you have no way of knowing whether the number was really a counterexample or just one that took many steps to reach 1.