($UDF:ty, $EXPR_FN:ident, $DOC:expr , $SCALAR_UDF_FN:ident) => {
        paste::paste! {
            // "fluent expr_fn" style function
            #[doc = $DOC]
            pub fn $EXPR_FN(arg: Vec<Expr>) -> Expr {
                Expr::ScalarFunction(ScalarFunction::new_udf(
                    $SCALAR_UDF_FN(),
                    arg,
                ))
            }