/**
* Folds this tree using the given monoid.
*
* @param f A transformation from this tree's elements, to the monoid.
* @param m The monoid to fold this tree with.
* @return The result of folding the tree with the given monoid.
*/
public <B> B foldMap(final F<A, B> f, final Monoid<B> m) {
return m.sum(f.f(root()), m.sumRight(subForest()._1().map(foldMap_(f, m)).toList()));
}
/**
* Maps the given function over this tree.
*
* @param f The function to map over this tree.
* @return The new Tree after the function has been applied to each element in this Tree.
*/
public <B> Tree<B> fmap(final F<A, B> f) {
return node(
f.f(root()), subForest().map(Stream.<Tree<A>, Tree<B>>map_().f(Tree.<A, B>fmap_().f(f))));
}