geneseo.cs.compiler
Class FiniteTransducer

java.lang.Object
  |
  +--geneseo.cs.compiler.FiniteTransducer

Direct Known Subclasses:

MinimLTransducer

public abstract class FiniteTransducer

extends java.lang.Object

Represents finite transducers in a fairly general way. At its heart, a transducer is something that accepts characters as input, and based on its internal state, returns a set of "action flags" that the client will presumably interpret as directions to do certain things. Sets of action flags are integers, with individual bits within the integer nominally representing individual flags. Bit fields, however, can also be used to encode actions with more than "do" vs "don't do" values. A transducer also updates its state on each input character. Transducers are table-driven, with tables indexed by state and character class, and containing next states and action flags. To be useful, a transducer needs a way of initializing its table and classifying characters, so this class is an abstract base class that must be extended to produce transducers for specific applications.

Constructor Summary

FiniteTransducer(Transition[][] t)
Initialize a finite transducer with its transition table.

Method Summary

abstract int	classify(int c) Classify a character.
int	getState() Find out what state a finite transducer is in.
int	process(int c) Process a character.
void	reset() Put a finite transducer into its start state.

Methods inherited from class java.lang.Object

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

Constructor Detail

FiniteTransducer

public FiniteTransducer(Transition[][] t)

Initialize a finite transducer with its transition table.

Parameters:

t - The transition table.

Method Detail

reset

public void reset()

Put a finite transducer into its start state.

getState

public int getState()

Find out what state a finite transducer is in. This message is most likely to be useful for debugging a transducer or tracing its actions; most interactions between clients and transducers should be communicated via action flags.

Returns:

The transducer's current state.

process

public int process(int c)

Process a character.

Parameters:

c - The character to process. The character is represented as an integer so that finite transducers can process data not normally thought of as characters, e.g., inputs from sensors.

Returns:

The action flags associated with the transition this character causes the transducer to take.

classify

public abstract int classify(int c)

Classify a character. Subclasses must define this method in such a way that it classifies whatever data the particular subclass's transducers process into classes appropriate to those transducers.

Parameters:

c - The character to classify. This "character" is represented by an integer so that finite transducers can process data not normally represented as characters, e.g., sensor inputs.

Returns:

The character's class.