public static Set <Set <I> > compute(Set <I> set)
{
switch (set)
{
case ExplicitSet <I> explicitSet: {
var subsets = new ExplicitSet <Set <I> >();
subsets.Elements.Add(Set <I> .EmptySet);
foreach (var elem in explicitSet.Elements)
{
var combos = subsets.Elements.ToHashSet();
foreach (var copy in combos.Select(s => ((ExplicitSet <I>)s).Elements.ToHashSet()))
{
copy.Add(elem);
subsets.Elements.Add(new ExplicitSet <I>(copy));
}
}
return(subsets);
}
case DerivedSet <I> derivedSet:
return(new DerivedSet <Set <I> >(s => s.IsSubset(set), derivedSet.GetCardinality().powerset(),
"x \\subseteq" + set.ToLaTeX()));
default:
return(null);
}
}
/// <summary>
/// Recursively collects all of the elements in the cartesian product
/// </summary>
/// <param name="sets">The groups to compute the cartesian product of</param>
/// <returns>A bag of all of the elements in the cartesian product</returns>
private static ConcurrentBag <Value.Tuple <I> > collectElements(ExplicitSet <I>[] sets)
{
var elements = new ConcurrentBag <Value.Tuple <I> >();
// If there is only one set, convert the identifiers to singleton arrays of elements
// containing their identifiers
if (sets.Length == 1)
{
Parallel.ForEach(sets[0].Elements, el =>
elements.Add(new Value.Tuple <I>(new[] { el }))
);
}
else
{
// Recursively collect all of the elements in the cartesian product of all sets except the first
var otherSets = new ExplicitSet <I> [sets.Length - 1];
Array.Copy(sets, 1, otherSets, 0, sets.Length - 1);
var otherGroupElems = collectElements(otherSets);
// Find all tuples containing this element as the first entry combined with all other tuples obtained
// recursively
Parallel.ForEach(sets[0].Elements, elem =>
Parallel.ForEach(otherGroupElems, el => {
var tup = new I[sets.Length];
tup[0] = elem;
Parallel.For(1, sets.Length, i => { tup[i] = el[i - 1]; });
var comb = new Value.Tuple <I>(tup);
elements.Add(comb);
})
);
}
return(elements);
}
