Interface defining an arbitrary bijective mapping from R^2 to R^2.
This interface provides methods to define an arbitrary bijective
mapping from R^2 to R^2, i.e. from the two-dimensional space of
real numbers onto itself, as is representable by the
::double floating point type. The mapping must be
bijective, i.e. map a pair of real numbers to exactly one other
pair of real numbers an vice versa, to facilitate a working
inverse. Bijectiveness also implies completeness, i.e. for every
pair of real numbers there must be another pair that is mapped
upon them.
