org.tensorics.core.tensor.variance

Class Covariant<C>

java.lang.Object

org.tensorics.core.tensor.variance.Covariant<C>

Type Parameters:

C - the type of the (contravariant!) coordinate

public class Covariant<C>
extends java.lang.Object

Coordinates inheriting from this class mark are treated as covariant axis. The type of 'variance' is defined, as in tensor-algebra, by transformation of the values of the tensor when transforming the basis of the values.

'Physical' vectors/quantities usually transform in such a way, that they transform inverse to the basis. For example, lets assume a vector of 3 values, representing karthesian coordinates in a certain base. If now the basis vectors would be multiplied by a factor, the values of the vector would have to be divided by the same factor. This transformation property is called 'contravariance'.

If the vectors would transform in the same way as the basis, we would say the vector (tensor in that direction) transforms 'covariant'. This is for example the case for tensors that represent transformations themselves.

Within the tensorics framework, because of the forementioned reasons, the contravariant case is considered as the default. Simply any object can be put as contravariant coordinate. On the other hand, covariant axes have to be marked explicitely, by inheriting from this class.

All sub classes are obliged to provide a public constructor with a single argument, taking the coordinate itself as an argument. This inheritance structure is necessary, to be able to have several covariant coordinates in one tensor (because tensorics treats coordinates of the same class as the same coordinate-dimension).

See Also:

http://en.wikipedia.org/wiki/ Covariance_and_contravariance_of_vectors

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Covariant(C coordinate) The single-argument constructor that has to be overriden by subclasses.

Method Summary

Modifier and Type	Method and Description
boolean	equals(java.lang.Object obj)
C	get() Retrieves the coordinate value from the covariant coordinate.
int	hashCode()
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

Covariant

protected Covariant(C coordinate)

The single-argument constructor that has to be overriden by subclasses. It takes the coordinate itself.

Parameters:

coordinate - the coordinate, which will be treated as a covariant axis

Throws:

java.lang.NullPointerException - if the given coordinate is null

Method Detail

get

public C get()

Retrieves the coordinate value from the covariant coordinate.

Returns:

the coordinate value

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

equals

public boolean equals(java.lang.Object obj)

Overrides:

equals in class java.lang.Object

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object