/// isEmpty - Returns true if the list is empty.
bool isEmpty() const { return !X; }
+ bool contains(const T& V) const {
+ for (iterator I = begin(), E = end(); I != E; ++I) {
+ if (*I == V)
+ return true;
+ }
+ return false;
+ }
+
/// isEqual - Returns true if two lists are equal. Because all lists created
/// from the same ImmutableListFactory are uniqued, this has O(1) complexity
/// because it the contents of the list do not need to be compared. Note