de.up.ling.irtg.algebra

Class EvaluatingAlgebra<E>

java.lang.Object

de.up.ling.irtg.algebra.Algebra<E>

de.up.ling.irtg.algebra.EvaluatingAlgebra<E>

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

GraphAlgebra

public abstract class EvaluatingAlgebra<E>
extends Algebra<E>

An algebra over a domain E that is defined by specifying the interpretation of the individual symbols. Subclasses of EvaluatingAlgebra will implement the evaluate(java.lang.String, java.util.List) method to assign a semantics to these symbols.

The algebra class then provides generic decomposition automata for these algebras. The states of these decomposition automata are values of E. They implement TreeAutomaton.getRulesBottomUp(int, java.util.List) by simply applying the algebra operation specified by the terminal symbol to the algebra objects specified by the child states.

Notice that the decomposition automata do not implement TreeAutomaton.getRulesTopDown(int, int), so you need to avoid using methods that access rules top-down. You should also expect that a parser using these generic decomposition automata are not particularly efficient.

See SetAlgebra for a use case of this class.

Author:

koller

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
EvaluatingAlgebra() Creates a new instance that will have a new signature.

Method Summary

Modifier and Type	Method and Description
TreeAutomaton	decompose(E value) Computes a decomposition automaton for the given value.
E	evaluate(Tree<String> t) Evaluates a term over the algebra's signature into an algebra object.
Signature	getSignature() Returns the signature of this algebra.
abstract E	parseString(String representation) Resolves the string representation of some element of the algebra's domain to this element.

Methods inherited from class de.up.ling.irtg.algebra.Algebra

getAllAlgebraClasses, getClassOfValues, hasOptions, readOptions, representAsString, setOptions, visualize, writeOptions

Methods inherited from class java.lang.Object

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

Constructor Detail

EvaluatingAlgebra

public EvaluatingAlgebra()

Creates a new instance that will have a new signature.

Method Detail

parseString

public abstract E parseString(String representation)
                       throws ParserException

Description copied from class: Algebra

Resolves the string representation of some element of the algebra's domain to this element. For instance, the method TreeAlgebra.parseString(java.lang.String) resolves the string "f(a,b)" into a tree with three nodes.

It is the job of an algebra class to keep track of the signature of the algebra. Many algebras have a potentially infinite domain (e.g. the string algebra can be used with arbitrary alphabets), so the algebra class should keep track of the symbols that were actually used in the current run of the program. The best practice is to update the signature each time the parseString method is called. The rest of the IRTG tool code takes care to call parseString of the respective algebra to obtain objects of type E, so this ensures that the signature is always up-to-date.

Specified by:

parseString in class Algebra<E>

Returns:

Throws:

ParserException

evaluate

public E evaluate(Tree<String> t)

Description copied from class: Algebra

Evaluates a term over the algebra's signature into an algebra object.

Overrides:

evaluate in class Algebra<E>

Parameters:

t - a term (= tree whose nodes are labeled with algebra operation symbols)

Returns:

decompose

public TreeAutomaton decompose(E value)

Description copied from class: Algebra

Computes a decomposition automaton for the given value. A decomposition automaton is a finite tree automaton which accepts exactly those terms over the algebra's signature which evaluate to the given value.

Overrides:

decompose in class Algebra<E>

Returns:

getSignature

public Signature getSignature()

Description copied from class: Algebra

Returns the signature of this algebra.

Overrides:

getSignature in class Algebra<E>

Returns: