On Aug 27, 2019, at 10:26 AM, Barry Revzin <barry.revzin@gmail.com> wrote:

On Tue, Aug 27, 2019, 12:02 PM Sophia Poirier via Std-Proposals <std-proposals@lists.isocpp.org> wrote:
Thanks, yes I have that as an alternate example in my longer notes.  My understanding is that it still suffers from the type-matching problem as traditional for loops.  Your example of:

for (const auto i : std::views::iota(0, count))

only works when count is an int.  Otherwise, if for example count is uint32_t, it would need to be:

for (const auto i : std::views::iota(uint32_t{0}, count)
or:
for (const auto i : std::views::iota(0u, count))
or:
for (const auto i : std::views::iota<uint32_t>(0, count))
or:
for (const auto i : std::views::iota<decltype(count)>(0, count))

or something along those lines, or you will get template instantiation failure compiler error.  I think that if std::views::iota had a constructor overload that was simply the second argument (count) with implicit zero start, then it would be a good option.  However I believe there is interest to reserve such an overload perhaps for infinite ranges?

thanks,
Sophia

This is true. But we can write a helper function to get the correct type of 0 so we don't need the ugliness at point of use:

template <std::integral T>
auto upto(T n) {
    return views::iota(T{0}, n);
}

We end up with:

for (const auto i : upto(count))

Barry

This could be the basis of an alternate library proposal, true.

- Sophia