[Haskell-cafe] Hoopl: Combining CheckingFuelMonad with State?

Justin Bailey jgbailey at gmail.com
Mon Jun 27 19:54:28 CEST 2011


I asked this question on StackOverflow and someone suggested using
StateT. Unfortunately I don't think I can really carry around the
state I'd like to:

  http://stackoverflow.com/questions/6495320/hoopl-how-can-i-combine-the-checkingfuelmonad-with-a-state-monad



On Fri, Jun 24, 2011 at 5:56 PM, Antoine Latter <aslatter at gmail.com> wrote:
> Hi Justin, this message might be better on the haskell-cafe list (or
> the excellent beginers list!).
>
> When you tried to write the get/put implementations, what problems
> were you running into?
>
> Antoine
>
> On Sat, Jun 25, 2011 at 7:50 AM, Justin Bailey <jgbailey at gmail.com> wrote:
>> I'd like to carry around some state when rewriting. It seems like
>> CheckingFuelMonad, etc. are set up to use with other monads but I
>> can't get the types to agree.
>>
>> Using MTL I've managed to come up with these types:
>>
>>> newtype RewriteOnce a = R (State Bool a)
>>>   deriving (Monad)
>>>
>>> instance MonadState s (CheckingFuelMonad RewriteOnce) where
>>>   get = undefined
>>>   put = undefined
>>
>>
>> But I cannot write the definitions for get and put. Is this possible
>> or am I misundersanding CheckingFuelMonad? Is there a better approach
>> altogether?
>>
>> Thanks in advance for any help!
>>
>> Justin
>>
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>>
>



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