All data structures in this library support insert, search, and remove, and have bidirectional iterators. The sorted data structures (everything but hash tables) support near-search operations: searching for the key greater or equal to, strictly greater than, lesser or equal to, or strictly less than, a given key. The tree data structures also support the selecting the nth element, which generally takes linear time, but only takes logarithmic time in path-reduction and weight-balanced trees. The API is designed with efficiency as a primary concern. For example, an insert call returns a boolean indicating whether or not the key was already present in the dictionary (i.e. whether there was an insertion or a collision), and a pointer to the location of the associated data. Thus, an insert-or-update operation can be supported with a single traversal of the data structure. In addition, the code is written to be very efficient, and almost all recursive algorithms have been rewritten to use iteration instead.