haskell - typeOf with type constructors of kind *->* / printing type of value from within program -

consider following :

module main  data tree = emptytree | node (tree a) (tree a) deriving (show, read, eq)   data container b = container{contfield :: b a} deriving (show)  result = container {contfield = node 'a' emptytree emptytree}  main =      print result 

if load ghci, following type of result :

*main> :t result result :: container char tree 

how can print type container char tree within program? trying adapt solution given @ haskell — typerep concrete type instance got stuck because not find way use typeof in conjunction type constructors of kind * -> *

[edit] : of methods in post have been deprecated in ghc 7.8.1 release notes version 7.8.1 :

typeable poly-kinded, making typeable1, typeable2, etc., obsolete, deprecated, , relegated data.oldtypeable. furthermore, user-written instances of typeable disallowed: use deriving or new extension -xautoderivetypeable, create typeable instances every datatype declared in module.

one possibility create typeable instance yourself. struggled bit creating tycon container, maybe there better way how it:

{-# language explicitforall #-} {-# language scopedtypevariables #-} {-# language derivedatatypeable #-} module main  import data.dynamic import data.typeable  data tree = emptytree | node (tree a) (tree a)     deriving (show, read, eq, typeable)  -- copy representation of type constructor  -- existing representation copytycon :: typeable => -> string -> tycon copytycon x = mktycon3 (tyconpackage tc) (tyconmodule tc)   tc = typereptycon (typeof x)  data dummy = dummy -- package/module names container     deriving (typeable)  data container b = container { contfield :: b }     deriving (show) instance (typeable a, typeable1 f) => typeable (container f)     typeof (container x) = mktyconapp (copytycon dummy "container")                                       [typeof (undefined :: a), typeof1 x]   result = container { contfield = node 'a' emptytree emptytree }  main =      print $ typeof result     print result 

take grain of salt, i'm not experienced typeable.