Prerequisits

#include <PowerSet.h>

using namespace polymake;

General case

template <class ElementType, class ElementComparator=BuildBinary<operations::cmp> > class PowerSet
  : public Set< Set<ElementType, ElementComparator> >;

As the name says, this is a set of subsets of a base set of ElementType. There is nothing special about this class, it was introduced mainly as a convenient shortcut for Set< Set<ElementType> > it is derived from. Due to the AVL tree data representation, the subsets appear in the lexicographical order. The base set is encoded only implicitly, as a union of all contained subsets.

The PowerSet class in its current implementation is definitely not the optimal tool for representing a power set. For a base set of non-negative integer numbers, you may get much better performance with a hashing container, e.g. std_ext::hash_set< Bitset >.

PowerSet has the same set of constructors as Set; it defines merely two own methods:

int PowerSet::insertMax(const GenericSet& s);
int PowerSet::insertMin(const GenericSet& s);
Both methods try to add s to the power set, preserving the condition that there may not be dependent subsets (one is included in another one) among the power set elements. Return the success code:
0 a subset equal to s was found, power set unchanged
-1 a subset including s (insertMax) or included in s (insertMin) was found, power set unchanged
1 s added to the power set, some other subsets might have been deleted: included in s (insertMax) or including s (insertMin.)
These methods are very expensive, as they iterate over the entire power set, performing the inclusion test for each element.
The same functionality is implemented much more efficiently in FacetList class, but with the same restriction as by Bitset: the base set has to be a contiguous range of non-negative integer numbers.

Special cases

Either a reference to the basic container whose lifetime is not shorter than that of the power set object, or a "bare" container type for a temporary object. See also the detailed discussion.
This is a convenience function, which allows to embed a temporary object into an expression without writing down its exact type. The result is identical to a direct call to the constructor of the corresponding class with the same arguments.
Please note that this and similar convenience functions always create an object parameterized with references to the input data (containers.) Sometimes, especially in a function return statement, you will need a reference-less variant; then you have to use the constructor.
This assertion is active only in the debugging compilation mode.

The following classes model power sets in some special but often occuring cases much more efficiently than PowerSet would do. The element subsets are not physically stored, but rather generated "on the fly" in the course of iteration over the power set.

These constructions can be applied to every class conforming to the STL container interface. However, the resulting power sets belong to the GenericSet family if and only if the base container is also a GenericSet, since only this assures that the generated subsets will appear in the lexicographical order. For the sake of brevity, we will nevertheless refer to the basic container as a set.

template <typename ContainerRef> class Subsets_of_1;
template <typename Container>
Subsets_of_1<const Container&> all_subsets_of_1 (const Container& set);
Set of one-element subsets of the given basic set. Each element is simply masqueraded as a set containing exactly one element.
template <typename ContainerRef> class Subsets_of_k;
template <typename Container>
Subsets_of_k<const Container&> all_subsets_of_k (const Container& set, int k);
Set of subsets of given cardinality. k should lie in the range [ 0, set.size() ].
template <typename ContainerRef> class Subsets_less_1;
template <typename Container>
Subsets_less_1<const Container&> all_subsets_less_1 (const Container& set);
Set of subsets of cardinality one less than the size of the basic set. That is, it is exactly one basic set element that is skipped in each subset.