The Something Awful forums is the obvious candidate here. It costs a flat 10$ to create an account. This generally makes trolling, spamming and scamming a losing proposition and broadly helps with the signal to noise ratio.
It traditionally leads to bigger executables and longer compile times. With modern compilers, both of these are non-issues for "most" reasonably-sized projects.
Unfortunately, you can't leverage template substitution rules with the lambda approach. And that's really necessary if you want to have actual powerful match expressions.
Then only unfortunate missing piece of the puzzle is that there's no trivial way to create a closure out of this, so it requires a bit more manual work to propagate local state to the visitor.
My gut feeling is that yes, this is pretty much self evident.
However, the interesting part of the paper is that they use that equivalency to propose that properties of polynomial regression are applicable to Neural networks, and draw some conclusions from that.
If I'm reading this right, the core of the argument is that since any continuous function is can be approximated via a taylor series expansion, then activation functions can be seen, in-effect, as polynomial in nature, and since a neuron layer is a linear transformation followed by an activation function, the the whole system is polynomial.
That's "technically" correct, but it feels like an academic cop-out. Interesting/useful transfer functions tend to be functions that take very large expansions to be approximated with any accuracy.
We are talking about a language that goes so far as to make sure it functions on systems where the size of a byte is not 8, or where memory is not necessarily linearly addressed. People tend to forget how shockingly flexible standard-compliant C++ code actually is.
C++, as a language, has never cared about the notion of "files". The entire standard is defined as a function of a "Translation Unit", which is an abstract notion that we tend to associate with "a single .cpp file" by nothing but convention.
Since modules operate at the language level, they need to operate on this notion, which precludes importing by file.
Hot take: success is almost always accompanied by a healthy dose of survivor bias. For each of these success stories, there are a lot of good people who did the exact same thing, but it didn't pan out because of timing, location, or other similar factors.