C++20 utilities for various kinds of tuples.
There’s some features I wanted that the standard tuple doesn’t implement, at least not portably. For example std::tuple<int,int> is not trivially copyable in libstdc++!
I wanted to automate structure packing by sorting a tuple’s types by size. Especially in templated/generic code, when you can’t actually perform this optimization by hand.
In this use-case, I want my tuple to be as std::trivially_.*_v as the equivalent handwritten struct would be, making the std::tuple (at least somewhat) suboptimal.
Additionally, because the layout of std::tuple is completely implementation dependent, it’s hard for my tuple sorting code to know how to actually order anything!
Prior to C++20, your regular std::tuple implementation took around 1,000 LOC or more, most of which is incidental complexity from having difficulty expressing key ideas in older C++ versions. But starting from scratch, a C++20 tuple implementation can be much closer to 200LOC.