Once a transformation function has been registered, creating an IntraMap from it is simple:
AstIntraMap *intramap; ... intramap = astIntraMap( "SqrTran", 2, 2, "" );
We simply use the astIntraMap constructor function and pass it the
name of the transformation function to use. This name is the same
(case sensitive) one that we associated with the function when we
registered it using astIntraReg ().
You can, of course, register any number of transformation functions and select which one to use whenever you create an IntraMap. You can also create any number of independent IntraMaps using each transformation function. In this sense, each transformation function you register effectively creates a new ``sub-class'' of IntraMap, from which you can create Objects just like any other class. However, an error will occur if you attempt to use a transformation function that has not yet been registered.
The second and third arguments to astIntraMap are the numbers of input and output coordinates. These define the Nin and Nout attributes for the IntraMap that is created and they must match the corresponding numbers given when the transformation function was registered.
The final argument is the usual attribute initialisation string. You
may set attribute values for an IntraMap in exactly the same way as
for any other Mapping (, and also see
).
AST A Library for Handling World Coordinate Systems in Astronomy