org.opentripplanner.routing.automata

Class Nonterminal

java.lang.Object

org.opentripplanner.routing.automata.Nonterminal

Direct Known Subclasses:

NTChoice, NTKleenePlus, NTKleeneStar, NTOptional, NTSequence, NTTrivial

public abstract class Nonterminal
extends Object

An abstract superclass for all nonterminals, which are models for instantiated NFAs. Also provides expression building methods which can be used via a static import. Thanks to Matt Might, whose self-described "toy Java library" inspired the use of Java syntax to build up automata: http://matt.might.net/articles/implementation-of-nfas-and-regular-expressions-in-java/ His library also contained a comment suggesting the more functional style provided here by the build() method.

Author:

abyrd

Constructor Summary

Constructors

Constructor and Description
Nonterminal()

Method Summary

Modifier and Type	Method and Description
abstract AutomatonState	build(AutomatonState in) Recursively builds a new graph of automaton states (an NFA) based on the model provided by this Nonterminal.
Nonterminal	chain(Object... objects)
static Nonterminal	choice(Object... objs)
Nonterminal	optional()
static Nonterminal	optional(Object... objs)
Nonterminal	or(Object that)
Nonterminal	plus()
static Nonterminal	plus(Object... objs)
static Nonterminal	seq(Object... objs)
Nonterminal	star()
static Nonterminal	star(Object... objs)
DFA	toDFA()
NFA	toNFA()

Methods inherited from class java.lang.Object

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

Constructor Detail

Nonterminal

public Nonterminal()

Method Detail

build

public abstract AutomatonState build(AutomatonState in)

Recursively builds a new graph of automaton states (an NFA) based on the model provided by this Nonterminal. This allows nonterminals to be reused in multiple expressions, or multiple times within a single expression. Because we allow epsilon moves in NFAs, every nonterminal can have a single entry and exit point (i.e. start and accept state).

Parameters:

entry - - the start state for the automaton to build

Returns:

the accept state of the newly constructed automaton

star

public Nonterminal star()

plus

public Nonterminal plus()

optional

public Nonterminal optional()

or

public Nonterminal or(Object that)

chain

public Nonterminal chain(Object... objects)

seq

public static Nonterminal seq(Object... objs)

star

public static Nonterminal star(Object... objs)

plus

public static Nonterminal plus(Object... objs)

optional

public static Nonterminal optional(Object... objs)

choice

public static Nonterminal choice(Object... objs)

toNFA

public NFA toNFA()

toDFA

public DFA toDFA()