Hacker News Reader

Comment by eru | Hacker News Reader

When talking informally, people often omit mentioning the base case when it's obvious or trivial.

Btw, your recursion doesn't necessarily need a terminating case.

See eg this definition of the list of Fibonacci numbers in Haskell:

    fibs :: [Integer]
    fibs = 1 : 1 : zipWith (+) fibs (tail fibs)

View on HN

That's not recursion. And reversing arrows on this category turns base cases into co-base, or start cases, (and these are still often called base cases in the literature), so it is still required.

Reversing arrows again, back to recursion, you have exactly the standard labeled bases case (well, cases in your code), and reversing arrows doesn't magically change algorithms or invent new structure, so it completely equivalent in the category.

For that code, the 1:1:... is exactly the terminating/starting point, reversing arrows in the category does nothing to change the requirements.

Strictly-speaking, that's corecursion.

Of course. But it's close enough as a reply to "your algorithm for multiplication involves doing multiplication?"

Reply on news.ycombinator.com