If that's the semantics you want, why not just add a check at the beginning of the loop? Compilers could add a warning advising the developer to do this if she

If that's the semantics you want, why not just add a check at the beginning of the loop? Compilers could add a warning advising the developer to do this if she doesn't care about partial results, anytime that they can't fully eliminate an .at() bounds check inside a loop.