Ideal Hash Array Mapped Tries: an Erlang functional datatype "The Hash Array Mapped Trie (HAMT) is based on the simple notion of hashing a key and storing the key in a trie based on this hash value. The AMT is used to implement the required structure efficiently. The Array Mapped Trie (AMT) is a versatile data structure and yields attractive alternative to contemporary algo- rithms in many applications. Here I describe how it is used to develop Hash Trees with near ideal characteristics that avoid the traditional problem, setting the size of the initial root hash table or incurring the high cost of dynamic resizing to achieve an acceptable performance." The quote above is from the paper "Ideal Hash Tries" by Phil Bagwell [2000]: @ARTICLE{Bagwell01idealhash, author = {Phil Bagwell}, title = {Ideal Hash Trees}, journal = {Es Grands Champs}, year = {2001}, volume = {1195} } http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.21.6279 http://lampwww.epfl.ch/papers/idealhashtrees.pdf http://en.wikipedia.org/wiki/Hash_array_mapped_trie This is an experiment in functional datatypes in Erlang. At some point I'll mature this into a persistent concurrent hash array mapped trie (ctrie).