"S.M.Kahrs" wrote: [snip] > I don't think this really solves the problem with the left unit > (not in general, and not for IO either), > it merely pushes it to a different place. [snip] Not being a category theorist I find this all a bit confusing. Can you give an example where with GHC and the fix I suggested you can show that the associative law has been broken?