float

numeric

to_field

evaluate

// defines required arguments "a" and "b", variadic argument "rest", and optional argument "c" with default value of lit(0)
create_args_struct!(FooArgs, a, b, *rest, c = 0)

// the generated struct would look like:
struct FooArgs<T> {
    a: T,
    b: T,
    rest: Vec<T>,
    c: T
}

// this will also be automatically implemented for FooArgs
impl<T> TryFrom<FunctionArgs<T>> for FooArgs<T> {
    fn try_from(args: FunctionArgs<T>) -> DaftResult<Self<T> {
        ...
    }
}

// then, you would use it like:
impl ScalarUDF for Foo {
    type Args<T> = FooArgs<T>;

    fn to_field(&self, inputs: FooArgs<ExprRef>) -> DaftResult<Field> {
        ...
    }
    
    fn evaluate(&self, inputs: FooArgs<Series>) -> DaftResult<Series> {
        ...
    }
}

Expr::children

Expr::with_new_children

evaluate/to_field