org.projog.core.predicate

Class PredicateKey

java.lang.Object

org.projog.core.predicate.PredicateKey

All Implemented Interfaces:

Comparable<PredicateKey>

public final class PredicateKey
extends Object
implements Comparable<PredicateKey>

Represents the structure of a Term.

Defines Terms by their name (functor) and number of arguments (arity). This "metadata" or "descriptor information" allows rules whose heads (consequences) share the same structure to be grouped together.

As Atom and Structure are the only subclasses of Term that can be the head (consequent) of a rule they are the only subclasses of Term that PredicateKey is intended to describe.

PredicateKeys are constant; their values cannot be changed after they are created.

Constructor Summary

Constructors

Constructor and Description
PredicateKey(String name, int numArgs)

Method Summary

Modifier and Type	Method and Description
int	compareTo(PredicateKey o) Ordered on name or, if names identical, number of arguments.
static PredicateKey	createForTerm(Term t) Returns a PredicateKey for the specified term.
static PredicateKey	createFromNameAndArity(Term t)
boolean	equals(Object o)
String	getName()
int	getNumArgs()
int	hashCode()
String	toString()
Term	toTerm()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

PredicateKey

public PredicateKey(String name,
                    int numArgs)

Method Detail

createForTerm

public static PredicateKey createForTerm(Term t)

Returns a PredicateKey for the specified term.

Parameters:

t - a term the returned PredicateKey should represent (needs to have a Term.getType() value of TermType.ATOM or TermType.STRUCTURE)

Returns:

a PredicateKey for the specified term.

Throws:

ProjogException - if t is not of type TermType.ATOM or TermType.STRUCTURE

createFromNameAndArity

public static PredicateKey createFromNameAndArity(Term t)

Parameters:

t - must be a structure named / where the first argument is the name of the predicate to represent and the second (and final) argument is the arity.

getName

public String getName()

getNumArgs

public int getNumArgs()

toTerm

public Term toTerm()

equals

public boolean equals(Object o)

Overrides:

equals in class Object

Parameters:

o - the reference object with which to compare.

Returns:

true if o is an instanceof PredicateKey and has the same name and number of arguments as this instance

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object

Returns:

name+"/"+numArgs

compareTo

public int compareTo(PredicateKey o)

Ordered on name or, if names identical, number of arguments.

Specified by:

compareTo in interface Comparable<PredicateKey>