24 Sep
2008
24 Sep
'08
1:48 p.m.
http://www.haskell.org/pipermail/libraries/2008-September/010623.html .. What one cannot do (in Haskell 98) is to have two instances of the same class, for the same types, in the same import hierarchy.
Of course, when you consider that Main, by definition, imports every module in the program directly or indirectly, this is pretty close to saying `instances are global'. Isn't it?
Close, but no cigar!-) The global view accepts strictly more programs than the Haskell 98 view (see the mesage I linked to for an example). It would also refuse some programs that Ghc (in non-Haskell 98 mode) accepts. And would stand in the way of looking for more precise instance import/export control (see both of my messages;-). Claus