Bulat Ziganshin wrote:
Language.Haskell.TH.Lib is full of definitions like this:
infixP p1 n p2 = do p1' <- p1
p2' <- p2
return (InfixP p1' n p2')
btw, such definitions can be simplified by using liftM/ap operations:
instance (Monad m, MyNum v) => MyNum (m v) where
(.+) = liftM2 (.+)
Such simplified forms then occur often enough that, in a scrapping
boilerplate kind of way, I would really like to be able to write
something like
instance (Monad m, MyNum v) => MyNum (m v) via lifting
or
lifted instance (Monad m, MyNum v) => MyNum (m v)
or
derived instance (Monad m, MyNum v) => MyNum (m v)
where all the operations from MyNum are obtained via applying the correct arity
liftM function from the Monad class.
Jacques
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