With a bit of fiddeling you can use every kind of bracket to basically make function calls in c++
Here are the links to the snippets, all compile and run
Rust: https://godbolt.org/z/bM3d7bG14
Only one of those is a function, get it right. () Call functions <> Specialize Templates, can be used to do compile time calls to things that behave like functions. [] Accesses elements {} Calls constructors, aka functions that do the initial setup.
Overloading these to do something else gets you in the naughty corner.
Edit: the implementation of the {} fuckery is no great. Just save the sum instead of all numbers.