Otherwise, returns rwnil and leaves the value of tr unchanged. Returns true if the insertion is successful, otherwise returns false . The function will return true unless the collection already holds an association with the equivalent key. It behaves exactly the same as insert . Returns true if there are no items in the collection, false otherwise.
Returns rwnil if there is no such association.
Returns rwnil if there is no such association. Returns the number of associations removed. Returns the number removed. If a collection is created off the heap, then you are responsible for deleting it.