jtp.fol
Class UnifyableList

java.lang.Object
  |
  +--java.util.AbstractCollection
        |
        +--java.util.AbstractList
              |
              +--jtp.fol.SubstitutableList
                    |
                    +--jtp.fol.UnifyableList

All Implemented Interfaces:

Collection, List, Serializable, Substitutable, Unifyable

public class UnifyableList

extends SubstitutableList

implements Unifyable

A List that implements the Unifyable interface. That is, it has elements that can be unified. UnifyableLists are often used to represent function terms.

See Also:

Serialized Form

Field Summary

Fields inherited from class jtp.fol.SubstitutableList

args

Fields inherited from class java.util.AbstractList

modCount

Method Summary

boolean	contains(Variable v) Checks if this Unifyable contains a given Variable (in that case, they cannot be unified).
Object	deReferenceVariables() Replaces all the variables in this Unifyable by their values.
Collection	getVariables(Collection target) Retrieves the variables in this Unifyable and places them into a provided target collection.
boolean	unify(Object o, List bindings) Attempts to unify with another object, that is find a variable assignment that will make the two objects equal.

Methods inherited from class jtp.fol.SubstitutableList

get, size, substitute, toString

Methods inherited from class java.util.AbstractList

add, add, addAll, clear, equals, hashCode, indexOf, iterator, lastIndexOf, listIterator, listIterator, remove, removeRange, set, subList

Methods inherited from class java.util.AbstractCollection

addAll, contains, containsAll, isEmpty, remove, removeAll, retainAll, toArray, toArray

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.List

addAll, contains, containsAll, isEmpty, remove, removeAll, retainAll, toArray, toArray

Method Detail

getVariables

public Collection getVariables(Collection target)

Description copied from interface: Unifyable

Retrieves the variables in this Unifyable and places them into a provided target collection.

Specified by:

getVariables in interface Unifyable

Parameters:

target - the collection to which the variables are added. If null, and this Unifyable contains variables, a new collection is created.

Returns:

the target collection. If target is null, and there are no variables, null is returned; if a new collection is created, it has to be modifyable.

deReferenceVariables

public Object deReferenceVariables()

Description copied from interface: Unifyable

Replaces all the variables in this Unifyable by their values. If a value is, in its turn, a variable, the process is repeated.

Specified by:

deReferenceVariables in interface Unifyable

Returns:

the copy of this Unifyable with all variables de-referenced. In many subclass implementations, this is returned if no variables needed to be dereferenced.

See Also:

Variable

contains

public boolean contains(Variable v)

Description copied from interface: Unifyable

Checks if this Unifyable contains a given Variable (in that case, they cannot be unified). The simplest (if not always the most efficient) implementation is to delegate u.contains(v) to u.getVariables(null).contains(v).

Specified by:

contains in interface Unifyable

Parameters:

v - the variable to look for

Returns:

true if the variable was found in this Unifyable.

unify

public boolean unify(Object o,
                     List bindings)

Description copied from interface: Unifyable

Attempts to unify with another object, that is find a variable assignment that will make the two objects equal. If the unification is sucessful, the state of the participating variables is changed, i.e. they receive values. These variables are added to the variable stack. If the function returned true, but the stack didn't grow, then the two objects were probably equal to begin with.

Specified by:

unify in interface Unifyable

Parameters:

o - the object to unify with.

bindings - the variable stack

Returns:

true if successful