re
Class NFA

java.lang.Object
  re.NFA

public class NFA
extends Object

A class to represent an NFA. You should create an NFA from a regular expression using this class. States are represented as numbers (with 0 always being the start state). Transitions can be lablled with 'a' - 'z', or '@' to indicate an epsilon transition. The constructor for NFA creates an automaton containing only state 0 and no transitions. The other NFA methods permit you to add new states and edges to the NFA, as well as to print out an NFA in a form suitable for the NFASimulator (or for viewing with dot).

Constructor Summary

NFA()
Create a new NFA with state 0.

Method Summary

void	addTransition(int start, int end, char c) Add a transition to the NFA.
int	newState() Add a new state to the NFA and return its id number.
void	printDot() Creates a file nfa.dot containing a graphical description of the NFA.
void	setAcceptState(int state) Set the accepting state for the NFA.
String	toString() Return a String representing the NFA in a way that can be read in by nfa.NFASimulator.

Methods inherited from class java.lang.Object

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

Constructor Detail

NFA

public NFA()

Create a new NFA with state 0.

Method Detail

setAcceptState

public void setAcceptState(int state)

Set the accepting state for the NFA. Must be a previously allocated state.

addTransition

public void addTransition(int start,
                          int end,
                          char c)

Add a transition to the NFA.

Parameters:

start - must be a valid state in the NFA

end - must be a valid state in the NFA

c - the character on the edge. 'a' <= c <= 'z', or c == '@' for epsilon

newState

public int newState()

Add a new state to the NFA and return its id number.

toString

public String toString()

Return a String representing the NFA in a way that can be read in by nfa.NFASimulator.

Overrides:

toString in class Object

printDot

public void printDot()

Creates a file nfa.dot containing a graphical description of the NFA. That file can then be processed with the dot utility.