Re: Kind error in GHC-7.4.1, works in GHC-7.2.2

Thank you for the explanation. I now understand the problem. I have rewritten the code using some parenthesis. Thanks, Roel 2012/2/10 Simon Peyton-Jones :

It should not have worked before.  Consider

       I#  $   3#

($) is a polymorphic function and takes two *pointer* arguments.  If we actually called it with I# and 3# as arguments we might seg-fault when we call the GC when allocating the box.

Polymorphic type variables (in this case in the type of ($)) can only be instantiated with boxed types.

Simon