Comment by quodlibetor

> Not much polars can do about that in Rust

I'm ignorant about the exact situation in Polars, but it seems like this is the same problem that web frameworks have to handle to enable registering arbitrary functions, and they generally do it with a FromRequest trait and macros that implement it for functions of up to N arguments. I'm curious if there are were attempts that failed for something like FromDataframe to enable at least |c: Col<i32>("a"), c2: Col<f64>("b")| {...}

https://github.com/tokio-rs/axum/blob/86868de80e0b3716d9ef39...

https://github.com/tokio-rs/axum/blob/86868de80e0b3716d9ef39...