com.svincent.moksa
Class Variable

java.lang.Object
  |
  +--com.svincent.moksa.WamObject
        |
        +--com.svincent.moksa.PrologTerm
              |
              +--com.svincent.moksa.Variable

All Implemented Interfaces:

Trailable

public class Variable

extends PrologTerm

Represents a Variable: a WAM term that contains (possibly) a reference to another WAM term.

Fields inherited from class com.svincent.moksa.PrologTerm

EmptyArray

Constructor Summary

Variable(PrologEngine _engine, java.lang.String _name)
Constructs a new Variable with the given name.

Method Summary

java.lang.Object	accept(PrologTermVisitor v, java.lang.Object parm) Allow PrologTermVisitor to access this PrologTerm.
void	bind(PrologTerm newValue) Binds this variable to the given new value.
PrologTerm	clonePrologTerm(java.util.Map objs)
PrologTerm	deref() Dereferences this PrologTerm, retrieving the PrologTerm that it represents.
java.lang.String	getName() Retrieves this Variable's name.
PrologTerm	getValue() Retrieves this Variable's value.
boolean	isVariable() Returns true iff this is a Variable.
protected void	tag(java.io.PrintWriter out) Writes a short human-readable representation of this object to the given Writer.
boolean	unify(PrologTerm that, boolean doBindings) Unification algorithm.
void	untrail() Unbinds the Variable

Methods inherited from class com.svincent.moksa.PrologTerm

clonePrologTerm, evaluateExpression, floatValue, getArity, getNameConstant, getPriority, intValue, isAtom, isCompoundTerm, isConstant, isEmptyList, isFloat, isInteger, isJavaObject, isList, isNonEmptyList, isStreamId, isStructure, printVariables, setPriority, unify, unifyWithoutBindings

Methods inherited from class com.svincent.moksa.WamObject

tag

Methods inherited from class java.lang.Object

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

Constructor Detail

Variable

public Variable(PrologEngine _engine,
                java.lang.String _name)

Constructs a new Variable with the given name. Note that by default, this Variable's value will not be null. Rather, it points to itself, by WAM convention.

(There are some good consequences that come out of this slightly odd convention)

Method Detail

getName

public java.lang.String getName()

Retrieves this Variable's name.

Overrides:

getName in class PrologTerm

getValue

public PrologTerm getValue()

Retrieves this Variable's value.

isVariable

public boolean isVariable()

Returns true iff this is a Variable.

Overrides:

isVariable in class PrologTerm

accept

public java.lang.Object accept(PrologTermVisitor v,
                               java.lang.Object parm)

Allow PrologTermVisitor to access this PrologTerm.

Overrides:

accept in class PrologTerm

deref

public PrologTerm deref()

Dereferences this PrologTerm, retrieving the PrologTerm that it represents. This has no effect except for Variables.

Unbound variables and all other PrologTerms return themselves.

Overrides:

deref in class PrologTerm

bind

public void bind(PrologTerm newValue)

Binds this variable to the given new value.

Returns:

true iff the binding was successful.

unify

public boolean unify(PrologTerm that,
                     boolean doBindings)

Unification algorithm. Can cause variables to become bound. (We will eventually have a rollback mechanism to undo these bindings.)

Overrides:

unify in class PrologTerm

Returns:

true iff the two PrologTerms successfully unify.

clonePrologTerm

public PrologTerm clonePrologTerm(java.util.Map objs)

Overrides:

clonePrologTerm in class PrologTerm

untrail

public void untrail()

Unbinds the Variable

Overrides:

untrail in class PrologTerm

tag

protected void tag(java.io.PrintWriter out)

Writes a short human-readable representation of this object to the given Writer.

Overrides:

tag in class WamObject