weakly_incrementable constraint while using iota_view

Question

To quickly create a for loop similar to python's for i in range(100), I could do:

for (auto const i : std::views::iota(0, 100))
{ /* ... */ }

However, CLion is warning me to add a std::weakly_incrementable constraint to my auto:

for (std::weakly_incrementable auto const i : std::views::iota(0, 100))
{ /* ... */ }

I know that the starting value of iota_view must be weakly_incrementable, and I would assume that auto i will create an i that is the same type of the starting value.

But is it true? Is it possible for it to create something of a totally different type (not even weakly incrementable)? And can I safely ignore the warning?

Answer 1

Is it possible for it to create something of a totally different type (not even weakly incrementable)? And can I safely ignore the warning?

According to the synopsis of iota_view in [range.iota.view]:

template<weakly_­incrementable W, semiregular Bound = unreachable_sentinel_t>
class iota_view : public view_interface<iota_view<W, Bound>> {
  //...
};

It is already constrained W must be weakly_incrementable. And since iota_view​::​iterator::operator*() returns the same type as W, you can ignore this warning.