Function proto_vulcan::relation::first

pub fn first<U, E, G>(
    list: LTerm<U, E>, 
    first: LTerm<U, E>
) -> InferredGoal<U, E, G> where
    U: User,
    E: Engine<U>,
    G: AnyGoal<U, E>, 

A relation such that the first is the first element of list.