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Polarisation greatly complicates everything, codes become rare and none is fully public domain.
Spectral line synthesis in polarised light has to be more or less reinvented, not from the physical point of view, but from the software engineering point of view. The underlying physics of the Stokes code Programming considerations Object orientation At the end of the millenium, processors have reached an unprecedented level of sophistication, clock speed is still steadily on the increase, memory expansion is almost unlimited, but software standards have hardly improved over the last 2 decades. The overwhelming part of scientific software presently in use has been written in Fortran, almost all of it prior to Fortran90. Modern software engineering concepts such as abstract data types, encapsulation, information hiding, generics, exception handling and many others are largely unknown to the scientific community. It provides powerful data abstraction mechanisms, hierarchical libraries, inheritance, polymorphism, and unique synchronisation and concurrent constructs.