Function polars::prelude::map_binary

pub fn map_binary<F>(
    a: Expr,
    b: Expr,
    f: F,
    output_type: SpecialEq<Arc<dyn FunctionOutputField + 'static>>
) -> Expr where
    F: 'static + Fn(Series, Series) -> Result<Series, PolarsError> + Send + Sync, 

Apply a closure on the two columns that are evaluated from Expr a and Expr b.