Comment by daxfohl

IME this is frequently a local optimum though. "Local" meaning, until some requirement changes or edge case is discovered, where some branching needs to happen outside of the loop. Then, if you've got branching both inside and outside the loop, it gets harder to reason about.

It can be case-dependent. Are you reasonably sure that the condition will only ever effect stuff inside the loop? Then sure, go ahead and put it there. If it's not hard to imagine requirements that would also branch outside of the loop, then it may be better to preemptively design it that way. The code may be more verbose, but frequently easier to follow, and hopefully less likely to turn into spaghetti later on.

(This is why I quit writing Haskell; it tends to make you feel like you want to write the most concise, "locally optimum" logic. But that doesn't express the intent behind the logic so much as the logic itself, and can lead to horrible unrolling of stuff when minor requirements change. At least, that was my experience.)