Okasaki v1.0.0 Okasaki.Implementations.ConstantDeque View Source
Deque is an implementation of Chris Okasaki’s Purely Functional Deque
This means that pushing and popping to both ends of the double-ended-queue happen in constant (O(1)) time.
For the paper upon which this is based: http://www.westpoint.edu/eecs/SiteAssets/SitePages/Faculty%20Publication%20Documents/Okasaki/jfp95queue.pdf