[Haskell-cafe] transformers problem: Could not deduce MonadTrans (StateT s) ??

[MigMit]

On 23 Jun 2012, at 21:27, Anton Kholomiov wrote:

> At last..
> 
> No, it wants me to define an instance for
> (StateT s) which is supposed to be defined
> be the authors of the library.
> 
> Actually I discovered that I have two libraries
> called transformers. 
> 
>    transformers-0.2.2.0
>    transformers-0.3.0.0
> 
> So when I'm doing 
> 
> import Control.Monad.Trans (0.2.2.0)

Ehm... seems like you're importing mtl instead of transformers. AFAIK there is no "Control.Monad.Trans" module in transformers.

> 
> I get the error
> 
> And when I'm doing
> 
> import Control.Monad.Trans.Class (0.2.2.0)
> 
> It compiles.
> 
> 
> Anton
> 
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