ubc.cs.JLog.Terms
Class jTerm

java.lang.Object
  extended by ubc.cs.JLog.Foundation.jType
      extended by ubc.cs.JLog.Terms.jTerm
All Implemented Interfaces:
iType, iUnifiable, iConsultable, iName, iTerm, iValue
Direct Known Subclasses:
iPredicate, jCommand, jCompoundTerm, jConjunctTerm, jInteger, jList, jObject, jReal, jVariable

public abstract class jTerm
extends jType
implements iTerm

This is the abstract base class for Prolog terms.

Author:
Glendon Holst

Field Summary
 
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
jTerm()
           
 
Method Summary
 int compare(jTerm term, boolean var_equal)
          The public interface for term comparision, it calls the protected compare that sub-classes must override.
protected abstract  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()
          Public member function which creates a copy of this term.
abstract  jTerm copy(jVariableRegistry vars)
          Internal member function which creates a copy of this term.
abstract  jTerm duplicate(jVariable[] vars)
          Creates a complete and entirely independant duplicate of this term.
abstract  void enumerateVariables(jVariableVector v, boolean all)
          Adds variables belonging to this term (or belonging to any sub-part of this term) to the jVariableVector
abstract  boolean equivalence(jTerm term, jEquivalenceMapping v)
          The public interface for evaluating term equivalence (i.e., structural similarity).
 java.lang.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 isConsultNeeded()
          Determine if cached values already exist and hence if consulting is required.
 void registerUnboundVariables(jUnifiedVector v)
          Adds any unbound variables belonging to this term (or belonging to any sub-part of this term) to the jUnifiedVector
abstract  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.
 boolean requiresCompleteVariableState()
          Call to determine if enclosing rule should record all variable states.
 java.lang.String toString()
           
abstract  java.lang.String toString(boolean usename)
          Produces a string identifying this term, suitable for display to the console.
abstract  boolean unify(jTerm term, jUnifiedVector v)
          Determines if this instance and term unify.
 
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
 

Constructor Detail

jTerm

public jTerm()
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
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()
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
Returns:
jTerm of the non-evaluated term bound to this instance.

getName

public java.lang.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
Returns:
String containing name of this instance.

compare

public int compare(jTerm term,
                   boolean var_equal)
The public interface for term comparision, it calls the protected compare that sub-classes must override.

Specified by:
compare in interface iTerm
Parameters:
term - the jTerm to compare with this instance of jTerm.
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.

compare

protected abstract int compare(jTerm term,
                               boolean first_call,
                               boolean var_equal)
The private member function for term comparision. Compares this instance to the provided jTerm. sub-classes must override.

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.

requiresCompleteVariableState

public boolean requiresCompleteVariableState()
Call to determine if enclosing rule should record all variable states. A rules goal only tracks variables which were unified, and relies on stack unwinding to unbind all variables. Terms such as cut, which jump back to the containing rules goal require that all variables are restored.

Specified by:
requiresCompleteVariableState in interface iTerm
Returns:
true if all variable bindings must be recorded by the rule containing this term. false otherwise. Normally returns false

registerUnboundVariables

public void registerUnboundVariables(jUnifiedVector v)
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
Parameters:
v - The jUnifiedVector where unbound variables are added to. This parameter is used to as output to the caller, not as input.

registerVariables

public abstract 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. all variables encountered should be unbound. After call, this term should not be modified in any way.

Specified by:
registerVariables in interface iTerm
Parameters:
v - The jUnifiedVector where variables are added to. This parameter is used to as output to the caller, not as input.

enumerateVariables

public abstract void enumerateVariables(jVariableVector v,
                                        boolean all)
Adds variables belonging to this term (or belonging to any sub-part of this term) to the jVariableVector

Specified by:
enumerateVariables in interface iTerm
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.

equivalence

public abstract 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
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 abstract 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
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.

duplicate

public abstract jTerm duplicate(jVariable[] vars)
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
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()
Public 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. Sub-classes need not override, only implement the abstract copy(vars) member function. copy is not as efficient as duplicate.

Specified by:
copy in interface iTerm
Returns:
jTerm which is an instantiated copy of this term.

copy

public abstract jTerm copy(jVariableRegistry vars)
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
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
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

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

toString

public abstract java.lang.String toString(boolean usename)
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
Returns:
String which is a textual representation of this term.

toString

public java.lang.String toString()
Overrides:
toString in class java.lang.Object