On Thu, Mar 05, 2015 at 03:43:30PM +0200, Konstantin Saveljev wrote:
I'm having some trouble with cyclic dependency.
[..]
So if I have a single module:
data A a = A (StateT MyState IO a) deriving (...) data MyState = MyState { st :: SomeType, ... } data SomeType = SomeType { f :: A (), ... }
With this setup the compiler is gonna tell us it doesn't know about MyState. And no matter how we shuffle these types within a file we are still getting some "unknowns"
Hello Konstantin. I just tried to feed this to ghci: data StateT a b = StateT a b data A a = A (StateT MyState (IO a)) data MyState = MyState { st :: SomeType } data SomeType = SomeType { f :: A () } and it works. I think the deriving clause is causing problems (not surprisingly); writing the instance out yourself should solve it.