UDCode - Does a set of code words form a uniquely decodable code? A code is a set of strings, called the _code words_. A code is "uniquely decodable" if any string S that is a concatenation of code words is so in _exactly one way_. For example, the code ("ab", "abba", "b") is _not_ uniquely decodable, because "abba" . "b" eq "ab" . "b" . "ab". But the code ("a", "ab", "abb") _is_ uniquely decodable, because there is no such pair of sequences of code words. UDcode contains a function "is_udcode" that tells whether a set of code words is a uniquely decodable code, and a function "ud_pair" that returns two sequences of code words whose concatenations are the same, if there is such a pair. Author: Mark Jason Dominus (mjd@plover.com) License: Public domain