at.jku.risc.stout.hoau.data

Class TermNode

java.lang.Object

at.jku.risc.stout.hoau.util.Printable

at.jku.risc.stout.hoau.data.TermNode

All Implemented Interfaces:

Cloneable

public class TermNode
extends Printable
implements Cloneable

A term node consists of a TermAtom and a Hedge.

Author:

Alexander Baumgartner

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	TermNode.TraverseCallBack This class may be used to traverse a term tree and execute an arbitrary operation on every node.

Field Summary

Fields

Modifier and Type	Field and Description
static TermAtom	nullAtom
static Hedge	nullHedge
static boolean	printUserFriendly The user friendly output form transforms lambda hedges to argument lists.

Constructor Summary

Constructors

Constructor and Description
TermNode(TermAtom atom, Hedge hedge) Instantiates a new term node.

Method Summary

Methods

Modifier and Type	Method and Description
TermNode	clone()
boolean	equals(Object other) This equality test performs an alpha equivalence test and also allows eta expansion in order to make the given TermNodes equal.
void	etaExpand(BoundVariable boundVar)
TermAtom	getAtom()
Hedge	getHedge()
boolean	hasFreeVar(Variable var) Checks whether a variable occurs freely inside inside the term.
boolean	isNullAtom() Tests whether the atom of this term node is the null atom.
void	print(Writer out)
TermNode	reduce(int maxSteps) Perform beta reduction with the given upper bound for recursion repetition to avoid endless recursion in untyped calculus.
TermNode	reduceHedges() Reduce unnecessary leading hedges.
void	setAtom(TermAtom atom) Null values are transformed to unique objects which represent the null value.
void	setHedge(Hedge hedge) Null values are transformed to unique objects which represent the null value.
void	substitute(BoundVariable from, BoundVariable to) Substitutes one bound variable by another bound variable.
void	substitute(Variable fromVar, TermNode toTerm) Substitutes a variable by a term and returns the result.
boolean	traverse(TermNode.TraverseCallBack callBack) Traverses the term tree and executes the callback function at every node.

Methods inherited from class at.jku.risc.stout.hoau.util.Printable

toString

Methods inherited from class java.lang.Object

getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

nullAtom

public static final TermAtom nullAtom

nullHedge

public static final Hedge nullHedge

printUserFriendly

public static boolean printUserFriendly

The user friendly output form transforms lambda hedges to argument lists. For instance (\x.(\y. x y)) will be displayed as \x.\y. x(y)
Default = true

Constructor Detail

TermNode

public TermNode(TermAtom atom,
        Hedge hedge)

Instantiates a new term node. null values are transformed to unique objects which represent the null value. So that no NullPointerException can occur.

See Also:

nullAtom, nullHedge

Method Detail

clone

public TermNode clone()

Overrides:

clone in class Object

equals

public boolean equals(Object other)

This equality test performs an alpha equivalence test and also allows eta expansion in order to make the given TermNodes equal.

Overrides:

equals in class Object

etaExpand

public void etaExpand(BoundVariable boundVar)

getAtom

public TermAtom getAtom()

getHedge

public Hedge getHedge()

hasFreeVar

public boolean hasFreeVar(Variable var)

Checks whether a variable occurs freely inside inside the term.

isNullAtom

public boolean isNullAtom()

Tests whether the atom of this term node is the null atom.

print

public void print(Writer out)
           throws IOException

Specified by:

print in class Printable

Throws:

IOException

reduce

public TermNode reduce(int maxSteps)
                throws NotNormalizableException

Perform beta reduction with the given upper bound for recursion repetition to avoid endless recursion in untyped calculus.

Throws:

NotNormalizableException

reduceHedges

public TermNode reduceHedges()

Reduce unnecessary leading hedges. For instance ((f(x))) will be reduced to f(x).

setAtom

public void setAtom(TermAtom atom)

Null values are transformed to unique objects which represent the null value. So that no NullPointerException can occur.

See Also:

nullAtom

setHedge

public void setHedge(Hedge hedge)

Null values are transformed to unique objects which represent the null value. So that no NullPointerException can occur.

See Also:

nullHedge

substitute

public void substitute(BoundVariable from,
              BoundVariable to)

Substitutes one bound variable by another bound variable.

substitute

public void substitute(Variable fromVar,
              TermNode toTerm)
                throws NotNormalizableException

Substitutes a variable by a term and returns the result.

Throws:

NotNormalizableException

traverse

public boolean traverse(TermNode.TraverseCallBack callBack)

Traverses the term tree and executes the callback function at every node.

See Also:

TermNode.TraverseCallBack