Levenshtein DFA in .NET

Question

Good afternoon,

Does anyone know of an \"out-of-the-box\" implementation of Levenshtein DFA (deterministic finite automata) in .NET (or easily translatable to i

Answer 1

We implemented this for apache lucene java, perhaps you could convert it to C# and save yourself time.

the main class is here: its just a builder to get Levenshtein DFAs from a string, using the Schulz and Mihov algorithm.

http://svn.apache.org/repos/asf/lucene/dev/trunk/lucene/src/java/org/apache/lucene/util/automaton/LevenshteinAutomata.java

the parametric descriptions (the precomputed tables) for Lev1 and Lev2 are here: http://svn.apache.org/repos/asf/lucene/dev/trunk/lucene/src/java/org/apache/lucene/util/automaton/Lev1ParametricDescription.java

http://svn.apache.org/repos/asf/lucene/dev/trunk/lucene/src/java/org/apache/lucene/util/automaton/Lev2ParametricDescription.java

you might notice these are generated with a computer, we generated them with this script, using Jean-Phillipe Barrette's great moman implementation (python) http://svn.apache.org/repos/asf/lucene/dev/trunk/lucene/src/java/org/apache/lucene/util/automaton/createLevAutomata.py

we generate the parametric descriptions as packed long[] arrays so that it won't make our jar file too large.

just modify the toAutomaton(int n) to fit your needs/DFA package. in our case we are using a modified form of the brics automaton package, where transitions are represented as unicode codepoint ranges.

efficient unit tests are difficult for this sort of thing, but here is what we came up with... it seems to be thorough and even found a bug (which was fixed immediately by the author!) in the moman implementation.

http://svn.apache.org/repos/asf/lucene/dev/trunk/lucene/src/test/org/apache/lucene/util/automaton/TestLevenshteinAutomata.java