I agree with this comment more or less, however I would like to point out that strlen{1,2,3} are all wrong, at least in the capacity that they take pointer diff

I agree with this comment more or less, however I would like to point out that strlen{1,2,3} are all wrong, at least in the capacity that they take pointer differences and return a size_t. In truth, `ptr_distance` and `return it - s;` should both be of type ptrdiff_t, which is not necessarily the same as size_t. In some ways this is why using an explicit index of type size_t that can be incremented is better, because you can avoid some type casting.