Before we start, it is worth taking a quick look at the Mapping class as a whole and some of the sub-classes it contains:
Mapping CmpMap DssMap GrismMap IntraMap LutMap MathMap MatrixMap PermMap PolyMap SlaMap SpecMap TimeMap UnitMap WcsMap ZoomMap Frame <various types of Frame>
The Frame sub-class has been separated out here because it is covered in detail in . We start by looking at the parent class, Mapping.
AST does not provide a function to create a basic Mapping
(i.e. the astMapping constructor does not exist). This is
because the Mapping class itself is ``virtual'' and basic Mappings are
of no use in themselves. The Mapping class serves simply to contain
the various specialised Mappings that exist.
However, it provides more than just a convenient heading for them
because it bestows all classes of Mapping with common properties
(e.g. attributes) and behaviour. By examining the Mapping
class, we are therefore examining the things that all other Mappings
have in common.
AST A Library for Handling World Coordinate Systems in Astronomy