Homepage: https://github.com/kisaragi-hiu/ordered-set.el
Author: Kisaragi Hiu
Updated:
Insertion-order sets
Sets are collections that does not permit duplicate objects, subject to some possibly arbitrary definition of "duplicate". This library currently always uses `equal'. Using lists as sets has performance issues, as list lookup is O(n). Hash tables provide O(1) lookup, but they don't preserve insertion order. This library attempts to provide the best of both worlds, at the cost of memory, by storing both a hash table and a list.