Function rustz::validation::apply4

pub fn apply4<A, B, C, D, R, F, E>(
    a: Validation<E, A>, 
    b: Validation<E, B>, 
    c: Validation<E, C>, 
    d: Validation<E, D>, 
    f: F
) -> Validation<E, R> where
    A: Clone,
    B: Clone,
    C: Clone,
    D: Clone,
    R: Clone,
    E: Clone + Semigroup,
    F: FnOnce(A, B, C, D) -> R,