Comment by TeMPOraL

Also:

- Does it destructively modify the argument, or return a substring? Or both?

- If it returns a substring, is it a view over the original string, or a fresh substring that doesn't share memory with the original?

- If it returns a fresh substring, how does it do it? Is it smart or dumb about allocations? This almost never matters, except when it does.

- How does it handle multibyte characters? Do locales impact it in any way?

With the languages we have today, a big part of the function contract cannot be explicitly expressed in function signatures. And it only gets worse with more complicated tools of abstraction.