@Override
public Vector<Object> flatten() {
return flatMap(
t ->
(t instanceof java.lang.Iterable)
? Vector.ofAll((java.lang.Iterable<?>) t).flatten()
: Vector.of(t));
}
Vector<Vector<T>> combinations(Vector<T> elements, int k) {
return (k == 0)
? Vector.of(Vector.empty())
: elements
.zipWithIndex()
.flatMap(
t ->
combinations(elements.drop(t._2 + 1), (k - 1))
.map((Vector<T> c) -> c.prepend(t._1)));
}
@Override
public Vector<Vector<T>> permutations() {
if (isEmpty()) {
return Vector.empty();
} else {
final Vector<T> tail = tail();
if (tail.isEmpty()) {
return Vector.of(this);
} else {
final Vector<Vector<T>> zero = empty();
// TODO: IntelliJ IDEA 14.1.1 needs a redundant cast here, jdk 1.8.0_40 compiles fine
return distinct()
.foldLeft(
zero,
(xs, x) ->
xs.appendAll(
remove(x)
.permutations()
.map((Function<Vector<T>, Vector<T>>) l -> l.prepend(x))));
}
}
}