Function left_distributes 

pub fn left_distributes<S: Debug + PartialEq + Clone, const N: usize>(
    items: &[S; N],
    f: impl Fn(S, S) -> S,
    g: impl Fn(S, S) -> S,
) -> Result<(), &'static str>

Defines the left distributive property

a(b+c) = ab + ac