fms_iterable VS range-v3

Good stuff! I am a fan of LINQ and see you took pains to make your library performant (a common complaint against LINQ). My take on a more C++-y way of doing this is https://github.com/keithalewis/fms_iterable. An iterable is a C++ iterator with explicit operator bool() const to detect the end. The downside is I have to figure out how to translate this into the standard set of LINQ operators. Nowhere near as complete as your work but my main use case is implementing numerical algorithms. Maybe you'll find a pony in there. :-)

See https://github.com/keithalewis/fms_iterable for some ideas in this direction.

It can be done: https://github.com/keithalewis/fms_iterable

std::ranges is in c++20, but you can pull in the library it was based on if you use 17 (https://github.com/ericniebler/range-v3)

What you are describing seems to be std::ranges. If you’re interested in understanding how to implement it, I recommend checking out the original reference implementation, rangev3. Trying to implement your own ranges framework is really good practice for learning how to do efficient, advanced generic programming in C++. I highly recommend it as a hobby learning project. But it’s also really, really hard to do correctly, so please just use the stdlib and/or rangev3 in any real project.

In C++23, there will be std::views::cartesian_product. It is already available in the range-v3 library, the one that the standard is based on.

/** * @brief Forwards value equivalent to the std::forward. * * Using cast instead of std::forward to avoid template instantiation. Used by * Eric Niebler in range library. * * @see https://github.com/ericniebler/range-v3 */

It uses a custom zip_iterator (which isn't very good, and you should really use the one from boost or from range-v3).

It contains very little functionality compared to the Eric Niebler’s reference implementation for my liking. Especially views. This will undoubtedly change in the future. But the point is moot, because they are not really supported the is no other option for now other than https://github.com/ericniebler/range-v3.

range-v3 is a great library allowing you to bridge the gap: https://github.com/ericniebler/range-v3

[range-v3](https://github.com/ericniebler/range-v3) which std::ranges was based on has the `to>()` which as far as I know is expected to get into c++23 :)