javaadvent_sample7.java

public static class FutureCompositions<V , A extends WannabeApplicative<V>>{

    private final Supplier<CompletableFuture<Outcome<A>>> _partial;

    private FutureCompositions(Supplier<CompletableFuture<Outcome<A>>> state)
    {
        _partial=state;
    }

    public FutureCompositions<V, A> binding(Partial<A> stage)
    {
        return new FutureCompositions<>(() -> stage.apply(_partial.get()));
    }

    public CompletableFuture<Outcome<V>> perform()
    {
        return _partial.get().thenApply(p -> p.mapR(WannabeApplicative::apply));
    }

    public static <V, A extends WannabeApplicative<V>> FutureCompositions<V, A> begin(A applicative)
    {
        return new FutureCompositions<>(() -> completedFuture(maybe(applicative)));
    }
}