Package org.tensorics.core.tensor.variance

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

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method 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