ubc.cs.JLog.Terms
Class jVariable

java.lang.Object
  ubc.cs.JLog.Foundation.jType
      ubc.cs.JLog.Terms.jTerm
          ubc.cs.JLog.Terms.jVariable

All Implemented Interfaces:

iType, iUnifiable, iConsultable, iName, iTerm, iValue

public class jVariable
extends jTerm

This is the class for Prolog variables.

Version:

%I%, %G%

Author:

Glendon Holst

Field Summary

protected jTerm	bound
protected String	name
protected int	proxy

Fields inherited from class ubc.cs.JLog.Foundation.jType

type

Fields inherited from interface ubc.cs.JLog.Terms.iTerm

EQUAL, GREATER_THAN, LESS_THAN

Fields inherited from interface ubc.cs.JLog.Foundation.iType

TYPE_ARITHMETIC, TYPE_ATOM, TYPE_BUILTINPREDICATE, TYPE_COMMAND, TYPE_COMPARE, TYPE_COMPOUND, TYPE_CONS, TYPE_IF, TYPE_INTEGER, TYPE_LIST, TYPE_NULLLIST, TYPE_NUMERICCOMPARE, TYPE_OBJECT, TYPE_OPERATOR, TYPE_OR, TYPE_ORPREDICATE, TYPE_PREDICATE, TYPE_PREDICATETERMS, TYPE_REAL, TYPE_TYPE, TYPE_UNARYARITHMETIC, TYPE_UNARYOPERATOR, TYPE_UNDEFINED, TYPE_VARIABLE

Constructor Summary

jVariable()
Constructor to create unnamed variables, such as "_".

jVariable(String n)

Method Summary

protected int	compare(jTerm term, boolean first_call, boolean var_equal) The private member function for term comparision.
void	consult(jKnowledgeBase kb) Consult the given jKnowledgeBase and cache any invariant values (those which would not change until the next time the jKnowledgeBase changes).
void	consultReset() Called when the jKnowledgeBase changes.
jTerm	copy(jVariableRegistry vars) Internal member function which creates a copy of this term.
jTerm	duplicate(jVariable[] vars) Creates a complete and entirely independant duplicate of this term.
void	enumerateVariables(jVariableVector v, boolean all) Adds variables belonging to this term (or belonging to any sub-part of this term) to the jVariableVector
boolean	equivalence(jTerm term, jEquivalenceMapping v) The public interface for evaluating term equivalence (i.e., structural similarity).
String	getIdentity() Get an unique indentifying name.
String	getName() Returns the name of this instance.
jTerm	getTerm() Returns the non-evaluated jTerm representation of this term.
jTerm	getValue() Return the value of this object after.
boolean	isBound()
boolean	isConsultNeeded() Determine if cached values already exist and hence if consulting is required.
boolean	isNamed()
boolean	isNamedForDisplay()
void	registerUnboundVariables(jUnifiedVector v) Adds any unbound variables belonging to this term (or belonging to any sub-part of this term) to the jUnifiedVector
void	registerVariables(jVariableVector v) Adds all variables belonging to this term (or belonging to any sub-part of this term) to the jUnifiedVector Should be called during the consultation phase by rules for their owned terms both head and base.
void	setBinding(jTerm b)
String	toString(boolean usename) Produces a string identifying this term, suitable for display to the console.
boolean	unify(jTerm term, jUnifiedVector v) Determines if this instance and term unify.

Methods inherited from class ubc.cs.JLog.Terms.jTerm

compare, copy, requiresCompleteVariableState, toString

Methods inherited from class ubc.cs.JLog.Foundation.jType

getType, objectToString

Methods inherited from class java.lang.Object

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

Field Detail

name

protected String name

bound

protected jTerm bound

proxy

protected int proxy

Constructor Detail

jVariable

public jVariable()

Constructor to create unnamed variables, such as "_".

jVariable

public jVariable(String n)

Method Detail

getValue

public jTerm getValue()

Description copied from interface: iValue

Return the value of this object after.

Specified by:

getValue in interface iTerm

Specified by:

getValue in interface iValue

Overrides:

getValue in class jTerm

Returns:

jTerm which represents the evaluated value of this instance, or the value bound to this instance, in the case of a variable.

getTerm

public jTerm getTerm()

Description copied from class: jTerm

Returns the non-evaluated jTerm representation of this term. Variables return the non-evaluated terms they are bound to.

Specified by:

getTerm in interface iTerm

Overrides:

getTerm in class jTerm

Returns:

jTerm of the non-evaluated term bound to this instance.

getName

public String getName()

Description copied from interface: iName

Returns the name of this instance.

Specified by:

getName in interface iName

Specified by:

getName in interface iTerm

Overrides:

getName in class jTerm

Returns:

String containing name of this instance.

getIdentity

public String getIdentity()

Get an unique indentifying name. Relies on the Object toString to tack on a number at the end of the string. If expectations are not met, this is still handled fairly gracefully.

Returns:

An identity string (based on the name and and id number from Object toString.

isNamed

public boolean isNamed()

isNamedForDisplay

public boolean isNamedForDisplay()

setBinding

public void setBinding(jTerm b)

isBound

public boolean isBound()

registerUnboundVariables

public void registerUnboundVariables(jUnifiedVector v)

Description copied from class: jTerm

Adds any unbound variables belonging to this term (or belonging to any sub-part of this term) to the jUnifiedVector

Specified by:

registerUnboundVariables in interface iTerm

Overrides:

registerUnboundVariables in class jTerm

Parameters:

v - The jUnifiedVector where unbound variables are added to. This parameter is used to as output to the caller, not as input.

compare

protected int compare(jTerm term,
                      boolean first_call,
                      boolean var_equal)

Description copied from class: jTerm

The private member function for term comparision. Compares this instance to the provided jTerm. sub-classes must override.

Specified by:

compare in class jTerm

Parameters:

term - the jTerm to compare with this instance of jTerm. if term is an unknown type then, if first_call is true, call term.compare(this,false) and return the negative result, otherwise return EQUAL.

first_call - true if just invoked by public compare member function. false otherwise.

var_equal - if var_equal is true, then unbound variables are considered equal. var_equal = false is standard prolog behavior.

Returns:

LESS_THAN if this instance is less than term, EQUAL if the two terms are equal, and GREATER_THAN if this instance is greater than term.

equivalence

public boolean equivalence(jTerm term,
                           jEquivalenceMapping v)

Description copied from interface: iTerm

The public interface for evaluating term equivalence (i.e., structural similarity).

Specified by:

equivalence in interface iTerm

Specified by:

equivalence in class jTerm

Parameters:

term - the jTerm to compare with this instance of jTerm.

v - v is the collection of equivalent variable pairs found. It should be empty when first calling this function.

Returns:

true if this instance is equivalent to term, false otherwise.

unify

public boolean unify(jTerm term,
                     jUnifiedVector v)

Description copied from interface: iUnifiable

Determines if this instance and term unify. Every variable which was previously unbound, but which becomes bound during the unification must register itself with the jUnifiedVector. It is the callers responsibility to deal with the unified vector.

Specified by:

unify in interface iUnifiable

Specified by:

unify in interface iTerm

Specified by:

unify in class jTerm

Parameters:

term - the term to unify with this instance.

v - the vector of variables bound during unification. Even if unification fails, this vector may contain recently bound vectors. This parameter is used to as output to the caller, not as input for unify.

Returns:

true if unification succeeded, false otherwise.

registerVariables

public void registerVariables(jVariableVector v)

Description copied from class: jTerm

Adds all variables belonging to this term (or belonging to any sub-part of this term) to the jUnifiedVector Should be called during the consultation phase by rules for their owned terms both head and base. all variables encountered should be unbound. After call, this term should not be modified in any way.

Specified by:

registerVariables in interface iTerm

Specified by:

registerVariables in class jTerm

Parameters:

v - The jUnifiedVector where variables are added to. This parameter is used to as output to the caller, not as input.

enumerateVariables

public void enumerateVariables(jVariableVector v,
                               boolean all)

Description copied from class: jTerm

Adds variables belonging to this term (or belonging to any sub-part of this term) to the jVariableVector

Specified by:

enumerateVariables in interface iTerm

Specified by:

enumerateVariables in class jTerm

Parameters:

v - The jVariabeVector where variables are added to. This parameter is used to as output to the caller, not as input.

all - If true, then all variables should register, otherwise only add non-existentially qualified variables.

duplicate

public jTerm duplicate(jVariable[] vars)

Description copied from class: jTerm

Creates a complete and entirely independant duplicate of this term. User should call only for terms for which registerVariables has already been invoked. Within duplicate, any other calls to duplicate should pass along the same vars array produced by registerVariables since the same duplication path previously taken by registerVariables should be taken by duplicate. This call is designed only for terms which belong to rules and are templates for instantiation. Any variables in the term should be unbound. As implied by the modification restrictions on registerVariables, terms and their children cannot change (especially during call!)

Specified by:

duplicate in interface iTerm

Specified by:

duplicate in class jTerm

Parameters:

vars - The user passes in a duplicate of the variable vector produced from the previous call to registerVariables. vars is produced from the jVariableVector by creating a single duplicate variable for each variable. Since this is created in the same order as the registerVariables, it is now efficient for jVariables to return their unique duplicate.

Returns:

jTerm which is an instantiated duplicate of this term.

copy

public jTerm copy(jVariableRegistry vars)

Description copied from class: jTerm

Internal member function which creates a copy of this term. This member function is designed to duplicate a term, but without the restrictions of the duplicate function. Should only be invoked by copy() or other copy(vars). Should only invoke other copy(vars) functions. Bound variables should return a copy of the bound term.

Specified by:

copy in interface iTerm

Specified by:

copy in class jTerm

Parameters:

vars - The registry of variables and their duplicates. Initially this is empty. As variables generate copies, they add themselves and their copy to the jVariableRegistry, and this is output from the function call. Any further calls with the same vars ensures that the same variable (in a different term) returns the same copy.

Returns:

jTerm which is an instantiated copy of this term.

consult

public void consult(jKnowledgeBase kb)

Description copied from interface: iConsultable

Consult the given jKnowledgeBase and cache any invariant values (those which would not change until the next time the jKnowledgeBase changes). Where possible, consultable objects should minimize computation and assume that any cached values are still accurate.

Specified by:

consult in interface iConsultable

Specified by:

consult in interface iTerm

Overrides:

consult in class jTerm

Parameters:

kb - the knowledge base which attempted proofs are based upon.

consultReset

public void consultReset()

Description copied from interface: iConsultable

Called when the jKnowledgeBase changes. Should set all cached values to dirty so that a following call to consult would perform a full lookup as required.

Specified by:

consultReset in interface iConsultable

Specified by:

consultReset in interface iTerm

Overrides:

consultReset in class jTerm

isConsultNeeded

public boolean isConsultNeeded()

Description copied from interface: iConsultable

Determine if cached values already exist and hence if consulting is required. If object does not knowimmediatly whether consulting is needed, then assuming it is required.

Specified by:

isConsultNeeded in interface iConsultable

Specified by:

isConsultNeeded in interface iTerm

Overrides:

isConsultNeeded in class jTerm

Returns:

false if cached values are valid, true otherwise, if consult should be called.

toString

public String toString(boolean usename)

Description copied from class: jTerm

Produces a string identifying this term, suitable for display to the console. param usename determines whether to display variables by name or identity. false is the default for displaying the term, true for displaying this term in a user query.

Specified by:

toString in interface iTerm

Specified by:

toString in class jTerm

Returns:

String which is a textual representation of this term.