Robert Will writes:
I think what Haskellers (and others) can do in most cases is to factor out platform dependent parts to mini-modules which have different implementations but the same interface. The version of such a module is choosen by the path it resides in during the build process. (Simplest case: the -i option of the compiler.)
I have to say, I dislike this approach to conditional compilation. - it puts the conditional in the build system rather than the source code, which means you have to look in the build system to find out what the code means. - it means if I want to ask questions like "hmm, how does this differ from the Windows version?" I have to go find the windows version of the file. - the interface to the module is duplicated, and nothing is checking that all your implementations have the same interface. OTOH, if you want to see a good example of #ifdefs gone wrong, take a look at GHC's native code generator. #ifdef can indeed be misused; that's not a reason to throw it out altogether. Cheers, Simon