Package org.projog.core.math

Class ArithmeticOperators

java.lang.Object

org.projog.core.math.ArithmeticOperators

public final class ArithmeticOperators
extends java.lang.Object

Maintains a collection of ArithmeticOperator instances.

This class provides a mechanism for "plugging in" or "injecting" implementations of ArithmeticOperator at runtime. This mechanism provides an easy way to configure and extend the arithmetic operations supported by Projog.

Each KnowledgeBase has a single unique ArithmeticOperators instance.

Field Summary

Fields

Modifier and Type	Field	Description
private KnowledgeBase	kb
private java.lang.Object	lock
private java.util.Map<PredicateKey,java.lang.String>	operatorClassNames
private java.util.Map<PredicateKey,ArithmeticOperator>	operatorInstances

Constructor Summary

Constructors

Constructor	Description
ArithmeticOperators(KnowledgeBase kb)

Method Summary

Modifier and Type	Method	Description
void	addArithmeticOperator(PredicateKey key, java.lang.String operatorClassName)	Associates a ArithmeticOperator with this KnowledgeBase.
void	addArithmeticOperator(PredicateKey key, ArithmeticOperator operator)	Associates a ArithmeticOperator with this KnowledgeBase.
private Numeric	calculate(Term term, Term[] args)
ArithmeticOperator	getArithmeticOperator(PredicateKey key)
Numeric	getNumeric(Term t)	Returns the result of evaluating the specified arithmetic expression.
private ArithmeticOperator	getPreprocessedArithmeticOperator(PredicateKey key, Term argument)
ArithmeticOperator	getPreprocessedArithmeticOperator(Term argument)
private ArithmeticOperator	instantiateArithmeticOperator(java.lang.String className)
private ArithmeticOperator	instantiateArithmeticOperator(PredicateKey key)

Methods inherited from class java.lang.Object

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

Field Detail

kb

private final KnowledgeBase kb

lock

private final java.lang.Object lock

operatorClassNames

private final java.util.Map<PredicateKey,java.lang.String> operatorClassNames

operatorInstances

private final java.util.Map<PredicateKey,ArithmeticOperator> operatorInstances

Constructor Detail

ArithmeticOperators

public ArithmeticOperators(KnowledgeBase kb)

Method Detail

addArithmeticOperator

public void addArithmeticOperator(PredicateKey key,
                                  ArithmeticOperator operator)

Associates a ArithmeticOperator with this KnowledgeBase.

Parameters:

key - The name and arity to associate the ArithmeticOperator with.

operator - The instance of ArithmeticOperator to be associated with key.

Throws:

ProjogException - if there is already a ArithmeticOperator associated with the PredicateKey

addArithmeticOperator

public void addArithmeticOperator(PredicateKey key,
                                  java.lang.String operatorClassName)

Associates a ArithmeticOperator with this KnowledgeBase.

Parameters:

key - The name and arity to associate the ArithmeticOperator with.

operatorClassName - The class name of the ArithmeticOperator to be associated with key.

Throws:

ProjogException - if there is already a ArithmeticOperator associated with the PredicateKey

getNumeric

public Numeric getNumeric(Term t)

Returns the result of evaluating the specified arithmetic expression.

Parameters:

t - a Term that can be evaluated as an arithmetic expression (e.g. a Structure of the form +(1,2) or a Numeric)

Returns:

the result of evaluating the specified arithmetic expression

Throws:

ProjogException - if the specified term does not represent an arithmetic expression

calculate

private Numeric calculate(Term term,
                          Term[] args)

getPreprocessedArithmeticOperator

public ArithmeticOperator getPreprocessedArithmeticOperator(Term argument)

Returns:

null if not found

getPreprocessedArithmeticOperator

private ArithmeticOperator getPreprocessedArithmeticOperator(PredicateKey key,
                                                             Term argument)

getArithmeticOperator

public ArithmeticOperator getArithmeticOperator(PredicateKey key)

Throws:

ProjogException - if not found

instantiateArithmeticOperator

private ArithmeticOperator instantiateArithmeticOperator(PredicateKey key)

instantiateArithmeticOperator

private ArithmeticOperator instantiateArithmeticOperator(java.lang.String className)