public interface Functor<T>
<R> Functor<R>
map(java.util.function.Function<? super T,? extends R> fn)
default Functor<T>
peek(java.util.function.Consumer<? super T> c)
<R> Functor<R> map(java.util.function.Function<? super T,? extends R> fn)
default Functor<T> peek(java.util.function.Consumer<? super T> c)