These are methods for the generic functions
shift,
rotate,
scalardilate,
affine,
flipxy and reflect
which perform geometrical operations on spatial objects,
and for the generic rescale which changes the unit of length.
The argument X should be an object of class "distfun"
representing the distance function of a spatial object Y.
Objects of class "distfun" are created by distfun.
The methods apply the specified geometrical transformation to
the original object Y, producing a new object Z
of the same type as Y. They then create a new distfun
object representing the distance function of Z.