[Haskell-cafe] Hopefully simple monad question

[Miguel Mitrofanov]

O, great. I didn't know you can write it this way.

Tom Nielsen wrote:
> newtype VMT m a =
>   VMT {runVMT :: StateT VMState m a}
>     deriving (Monad, MonadIO, MonadTrans, TransM, MonadState VMState)
> 
> works  here (ghc-6.10.3)
> 
> On Wed, Sep 16, 2009 at 11:42 AM, Miguel Mitrofanov
> <miguelimo38 at yandex.ru> wrote:
> 
>> newtype VMT m a =
>>  VMT {runVMT :: StateT VMState m a}
>>    deriving (Monad, MonadIO, MonadTrans, TransM)
>>
>> Unfortunately, you can't automatically derive MonadState, since it's a
>> multi-paremeter type class. You'll have to write down the derivation
>> yourself.
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