public IEnumerable <VariableLetterGroup> UniquePermutations()
{
VariableLetterGroup vlg = this.RankLetters();
foreach (VariableLetterGroup v in vlg.Permutations())
{
if (v.IsOrderedAccordingToLetterRanks())
{
yield return(v);
}
}
}
public IEnumerable <VariableLetterGroup> Permutations()
{
int letters_length = _letters.Count;
for (int i = 0; i < letters_length; i++)
{
if (letters_length == 1)
{
yield return(this);
}
else
{
VariableLetterGroup res = new VariableLetterGroup(_letters[i]);
VariableLetterGroup vlg_to_permute = new VariableLetterGroup(_letters);
vlg_to_permute.RemoveAt(i);
foreach (VariableLetterGroup vlg_permuted in vlg_to_permute.Permutations())
{
yield return(res + vlg_permuted);
}
}
}
}