Take vector for example, the size() function returns, guess what, the size of the vector.
So I should resort to guesswork and not even read the code, let alone hope for comments?
What if it's not actually vector that I want to use, but something that appears to be very like it, so I assume you wrote it to behave the same way, but for very good reasons, you wrote some things differently.
Suppose I want to use noCommentsBecauseYouShouldJustKnowFromTheCodeVector and call its size() function?
Tried it, it said 16 every time no matter what was in the vector - how do I know whether it's meant to return the element count or the size of the "vector" pointer in bytes? (Or some other calculation with some magnitude, such as capacity or memory usage?)
Also, what happens if the vector is null/uninitialized? Is that the same as when it's empty? For whatever language I use?
How big can its value be? (When it's valid / ever)
Can it be negative?
Are all values unambiguous?
Is it thread-safe?
Is there something else I may have called which will already contain the size value, so I can re-use it to save calling size() now?
Why am I using this vector anyway? Isn't there something better? (And if not, why not? Because there could be a really good reason, which I might not guess.)