public override String ToString()
{
int i;
StringBuilder s = new StringBuilder();
int arity = elems.Length;
s.Append("{");
for (i = 0; i < arity; i++)
{
if (i > 0)
{
s.Append(",");
}
s.Append(elems[i].ToString());
}
s.Append("}");
return s.ToString();
}