11 lines
322 B
Haskell
11 lines
322 B
Haskell
|
class Monad m => Logger m where
|
||
|
|
write :: String -> m ()
|
||
|
|
|
||
|
|
instance Logger IO where write = putStr
|
||
|
|
instance a ~ String => Logger (Writer a) where write = tell
|
||
|
|
|
||
|
|
verbose2 f x y = write (show x ++ " " ++
|
||
|
|
show y ++ " ==> " ++
|
||
|
|
show res ++ "\n") >> return res
|
||
|
|
where res = f x y
|