Theoretical Aspects of Lexical Analysis/Exercise 3

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Revision as of 06:10, 22 March 2009 by Root (talk | contribs) (DFA)

Use Thompson's algorithm to build the NFA for the following regular expression. Build the corresponding DFA and minimize it.

  • ((ε|a)b)*

NFA

The following is the result of applying Thompson's algorithm.


DFA

Determination table for the above NFA:

In α∈Σ move(In, α) ε-closure(move(In, α)) In+1 = ε-closure(move(In, α))
- - 0 0, 1, 2, 3, 4, 6, 8 0
0 a 5 5, 6 1
0 b 7 1, 2, 3, 4, 6, 7, 8 2
1 a - - -
1 b 7 1, 2, 3, 4, 6, 7, 8 2
2 a 5 5, 6 1
2 b 7 1, 2, 3, 4, 6, 7, 8 2
Graphically, the DFA is represented as follows:


Given the minimization tree to the right, the final minimal DFA is:


The minimization tree is as follows.