O(1) only if you're working in a language with length-stored strings (like Pascal[0]), right?

In something like C with its generic strings[1], it would surely have to be O(n) since you have to scan the entire string to calculate its length?

(I have always been terrible at big-O, mind.)

[0] There's probably more of them by now.

[1] ie. not a specific length-stored string type.

Yes. But that's a known misfeature of C and no other language does it like that. Plus I kind of meant arbitrary byte strings where you can have embedded zeroes and thus have to know the length.