Theoretical Aspects of Lexical Analysis/Exercise 4: Difference between revisions

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


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{{CollapsedCode|Minimization tree|
{{CollapsedCode|Minimization tree|
[[image:aula3p4mintree.jpg|200]]
[[image:aula3p4mintree.jpg|350px]]
}}
}}


The tree expansion for non-splitting sets has been omitted for simplicity ("a" transition for non-final states and the {0, 2} "a" and "b" transitions. The final states are all indistinguishable, regarding both "a" or "b" transitions (remember that, at this stage, we assume that individual states -- i.e., the final states -- are all indistinguishable).  
<!--The tree expansion for non-splitting sets has been omitted for simplicity ("a" transition for non-final states and the {0, 2} "a" and "b" transitions. The final states are all indistinguishable, regarding both "a" or "b" transitions (remember that, at this stage, we assume that individual states -- i.e., the final states -- are all indistinguishable).  
 
-->
Given the minimization tree above, the final minimal DFA is as follows:
Given the minimization tree above, the final minimal DFA is as follows:



Revision as of 07:53, 24 June 2016

Problem

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

  • (a|b)*abb(a|b)*

Solution

The non-deterministic finite automaton (NFA), built by applying Thompson's algorithm to the regular expression (a|b)*abb(a|b)* is the following:

NFA
b)*abb(a

Applying the determination algorithm to the above NFA, the following determination table is obtained:

Determination table

{

Graphically, the DFA is represented as follows:

DFA
b)*abb(a

The minimization tree is as follows:

Minimization tree

Given the minimization tree above, the final minimal DFA is as follows:

Minimal DFA
b)*abb(a