10 :! $HC $HC_OPTS -no-recomp -c A.hs
17 -- swap A2 for A, compile & reload
19 :! $HC $HC_OPTS -no-recomp -c A.hs
21 -- the system should ignore the compiled version and compile its own.
27 -- pick up newly compiled A
34 -- remove A.o: system should recompile A