I have come in need for a grammar parser in python (context-free). While there are plenty in python, many of them are very undocumented, some seem to have become orphaned projects and `yapps2` and `pyparsing` that I tried seem to be a bit limited for what I need them (or most probably I'm a noob). So, also in order to refresh my memory on grammars, I decided to make my own parser in python.
The first step was, as I saw it to go back to the roots, to finite-state machines. It happened that it is quite a bit of fun especially because it allows me to have a dip into `graphviz` and `pydot` for pretty plotting the state machines.
Here are some examples from "Elements of the Theory of Computation - H.Lewis, Ch. Papadimitriou, 2nd ed.
The first one is for the language L(M) = { w \in (a,b)* : w has an even number of b's}
And the second one decides the language L(M) = { w \in (a,b)* : w does not have three consecutive b's }
And here is the code: https://gist.github.com/mmxgn/5973875
