me.jaimegarza.syntax.model.graph

Class Dfa

java.lang.Object

me.jaimegarza.syntax.model.graph.DirectedGraph<DfaNode>

me.jaimegarza.syntax.model.graph.Dfa

public class Dfa
extends DirectedGraph<DfaNode>

Deterministic finite automaton. A directed graph without ε-transitions, with cycles, and multiple final states

Author:

jgarza

Field Summary

Fields inherited from class me.jaimegarza.syntax.model.graph.DirectedGraph

nodes, regex

Constructor Summary

Constructors

Constructor and Description
Dfa()

Method Summary

Modifier and Type	Method and Description
protected DfaNode	findNodeByClosure(Set<NfaNode> closure) Locate a node in the dfa by examining each node's ε-closure
void	generateFromNfa(Nfa graph) Generate a DFA out of a NFA.
DfaNode	getStart() Get the starting node
protected boolean	isClosureFinal(Set<NfaNode> closure) Is a given ε-closure final? We know that a ε-closure is final if any of the nfa nodes is an accept node
DfaNode	newNode(Set<NfaNode> closure) Create a dfa node with the given ε-closure.

Methods inherited from class me.jaimegarza.syntax.model.graph.DirectedGraph

getNode, getNodes, getRegex, layout, setRegex, toHtmlString, toString, V

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

Dfa

public Dfa()

Method Detail

newNode

public DfaNode newNode(Set<NfaNode> closure)

Create a dfa node with the given ε-closure. The ε-closure is usually obtained from a Nfa node's Node.eclosure() method.

Parameters:

closure - is the closure coming from a NFA

Returns:

the new node

findNodeByClosure

protected DfaNode findNodeByClosure(Set<NfaNode> closure)

Locate a node in the dfa by examining each node's ε-closure

Parameters:

closure - is the ε-closure to be checked against all nodes

Returns:

the node, or null if not existent.

isClosureFinal

protected boolean isClosureFinal(Set<NfaNode> closure)

Is a given ε-closure final? We know that a ε-closure is final if any of the nfa nodes is an accept node

Parameters:

closure - is a ε-closure of nodes to check

Returns:

true if any node in the closure is an accepting node

generateFromNfa

public void generateFromNfa(Nfa graph)

Generate a DFA out of a NFA. The steps are as follows:

1. Create a new DfaNode from the initial NFA starting state. Compute the ε-closure from the initial state.
2. Iterate all the nodes and all their symbol transitions to create new ε-closures. If the closures already exist in the DFA, use the found state with such ε-closure, otherwise create a new DFA state with the given ε-closure.

Parameters:

graph - is the nfa

getStart

public DfaNode getStart()

Get the starting node

Returns:

the starting dfa node