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Comment by esaym | Hacker News Reader

Believe it or not, I once interviewed for a cryptography firm and they had me look over some code samples to improve them. Some of my improvements were just what you did. But they stopped me mid way through and said that the "standard" they are required to follow only allows one return statement and it had to be at the end of the function... Don't know what standard it was, whether their own or some 3rd party compliance.

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I've heard this argument (I like a single exit point) before, but I don't really understand it, I'd love for someone to explain why they prefer it, if they do.

I think the main reason returning early works so well is that often times, when you're returning different values, it's because you quickly have an answer (often times that something is invalid) for particular inputs. Generally though, there is "real work" to be done after validating or normalizing your inputs.

If that's not true, you're probably trying to do too many things at once, and the different pieces should be broken into separate functions.

In the specific case of crypto, maybe they are concerned about leaking information through timing if they return early? Though even if you have only one exit point, that alone does not in any way guarantee that timing differences won't occur. For that, I think the same work must be done always and only at the very end it is decided whether or not the result is valid. Something like that. So maybe they have some other reason. Maybe it's just cargo cult programming.

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