[Haskell-cafe] closed classes [was: Re: exceptions vs. Either]

MR K P SCHUPKE k.schupke at imperial.ac.uk
Thu Aug 12 04:13:12 EDT 2004

Just wondering, but what exacly is the problem with this open/closed stuff?
As far as I understand it new instances can be added to classes in Haskell
(because they are open)... But its not like instances can be added at link
time, and all the instances that you wish to be considered _must_ be
imported into the current module! That means if we (for example) used
two pass compilation we could gather all the instances together first
and know that we have all instances for a given class before considering
any resolution of overlapping instances. Why is this not done?
(personally I don't mind if compilation takes longer if it makes coding


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