private static IEnumerator <IImmutableList <T> > AllChoiceCombinationsOfRemainder <T>(this IEnumerator <IEnumerable <T> > sequenceOfChoices)
{
if (!sequenceOfChoices.MoveNext())
{
yield return(ImmutableList.Create <T>());
yield break;
}
var headChoices = sequenceOfChoices.Current;
var tailChoices = sequenceOfChoices.AllChoiceCombinationsOfRemainder();
using (var e = tailChoices) {
while (e.MoveNext())
{
var tailChoice = e.Current;
foreach (var headChoice in headChoices)
{
yield return(tailChoice.Insert(0, headChoice));
}
}
}
}
