package org.psjava.util;

import org.psjava.ds.array.PSArray;

import org.psjava.ds.array.MutableArrayFromIterable;

import java.util.function.Predicate;

public class SubSetIterable {

public static <T> Iterable<Iterable<T>> create(final Iterable<T> superSet) {

final PSArray<T> array = MutableArrayFromIterable.create(superSet);

Assertion.ensure(array.size() <= 30, "too big set to iterate sub set");

return ConvertedIterable.create(ZeroTo.get(1 << array.size()), new Converter<Integer, Iterable<T>>() {

@Override

public Iterable<T> convert(final Integer bits) {

// Cannot get size of the sub st at this time. Because we use filter way

return ConvertedIterable.create(FilteredIterable.create(ZeroTo.get(array.size()), new Predicate<Integer>() {

@Override

public boolean test(Integer index) {

return IntBitUtil.get(bits, index);

}

}), new Converter<Integer, T>() {

@Override

public T convert(Integer index) {

return array.get(index);

}

});

}

});

}

private SubSetIterable() {

}

}