Hi. Christopher Howard писал 21.12.2012 14:27:
instance (Monoid a, Monoid b, Monoid c, Monoid d) => Monoid (Socket4 a b c d) where mempty = Socket4 mempty mempty mempty mempty Socket4 a b c d `mappend` Socket4 w x y z = Socket4 (a `mappend` w) (b `mappend` x) (c `mappend` y) (d `mappend` z)
data Socket 5 a b c d e... et cetera --------
Seeing as the pattern here is so rigid and obvious, I was wondering: is it possible to abstract this even more? So I could, for instance, just specify that I want a Socket with 8 types, and poof, it would be there? Or is this as meta as we get? (I.e., without going to something like Template Haskell.)
Something like data a ::: b = a ::: b infixl 5 ::: instance (Monoid a, Monoid b) => Monoid (a ::: b) where ... So, Monoid instance for, say, (a ::: b ::: c) == ((a ::: b) ::: c) will (should) be inferred automatically. WBR, Ilya Portnov