While at it, I suppose it's straightforward to implement arbitrary-precision integers and decimals in today's Rust; there are several crates for that. There's also a `tailcall` crate that apparently implements TCO [1].

[1]: https://docs.rs/tailcall/latest/tailcall/

Oh, I do know you can have arbitrary precision. I'm the author of realistic, which isn't "just" arbitrary precision it's an approximation of the computable reals as well, which is sometimes just enough more power than you'd hardly notice you have arbitrary precision too.

https://crates.io/crates/realistic