reAnimator, Visualizing Regular Expressions
I really loved this one, reAnimator is a very nice Regular Expressions visualisation tool created with openLazlo Plateform, compiled to Flash and it uses AJAX and JSON to request the FSAs and the graphs, the backend is written in C and Python. You can set your pattern and then test it, the graphics will display in real time how regular expression are proceeded in a nondeterministic finite-state automaton and a deterministic finite-state automaton. You can find more explanation in this blog entry.
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