Adrian Hey wrote:
The latter is probably true, in a strict technical sense. But I can't see a way to live without them and keep modularity. In any case, I don't think there's any reason to force programmers "wear the hair shirt" in this respect (other than dogma and superstitious fear about the evils of "global variables" :-)
I agree about not wearing a hair-shirt, but how do you propose to solve the multiple import problem: B imports A, C imports A, D imports B & C. Now the top level inits (a <- computation) in A, do they happen once, defining the same init A.a, do they happen twice, perhaps initialising B.A.a and C.A.a, do they happen twice, meaning that 'a' may have different values depending on whether it is accessed from B or C? for example: module A where a <- newChan 0 module B where import A b <- do {writeChan A.a 7;return ()} module C import A c <- do {writeChan A.a 6;return ()} module D import A import B d <- readChan A.a does this mean the same as: module D' import B import A d <- readChan A.a Should values really depend on the order of includes? Even if you limit things to just newChan in top level '<-' you still don't know if A.a in B the same A.a in C. Perhaps it is enough to say A.a only exists once no matter how many times it is directly or indirectly imported? Keean.