@Override
public Array<T> slice(long beginIndex, long endIndex) {
if (beginIndex >= endIndex || beginIndex >= length() || isEmpty()) {
return empty();
}
if (beginIndex <= 0 && endIndex >= length()) {
return this;
}
final int index = Math.max((int) beginIndex, 0);
final int length = Math.min((int) endIndex, length()) - index;
final Object[] arr = new Object[length];
System.arraycopy(delegate, index, arr, 0, length);
return wrap(arr);
}
@Override
public Vector<Vector<T>> combinations(int k) {
class Recursion {
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)));
}
}
return new Recursion().combinations(this, Math.max(k, 0));
}
@Override
public Array<Array<T>> combinations(int k) {
return Combinations.apply(this, Math.max(k, 0));
}
