Being able to specify the extensions required in a source file would be very useful in a range of cases. Very often helping other people with Haskell (in the case where they are trying to use someone else's module) is just a question of saying "try '-98'" or "try '-fglasgow-exts'" or whatever.
ghc and nhc98 already support this. ghc's mechanism is {-# OPTIONS -fglasgow-exts ... etc #-} at the top of the file - but there are quite a few restrictions on what flags are accepted in that pragma. nhc98's mechanism is {-# OPTIONS_COMPILE -nkpat ... etc #-} anywhere in the file, which has no restrictions on the options it accepts - you can use anything that can appear on the commandline. Incidentally, nhc98 also recognises the form {-# OPTIONS_LINK -L/usr/local/lib -lreadline ... etc #-} for extra link options, which are accumulated from all modules specified on the commandline. Regards, Malcolm