[Haskell-cafe] question about interruptable state runner

[Heinrich Apfelmus]

Alexander V Vershilov wrote:
> 
> I'm writing a small tcp server with that can handle connections and
> answer by rules writen in a small script that can be interpreted by server.
> For this purpose I've written an interpreter that has type
> 
>   ErrorT MyError (StateT ScriptState IO)
> 
> so I can call "native" IO function in that script, and define new one.
>   I can run this script with runState (runErrorT (...)) oldState.
> 
> But there is one problem: in script i should be able to call functions that
> will stop script interpretation and wait for some server event. To continue
> interpretation. 
> 
> Can smb give an advice what is the best way to do it?

Basically, you want to stop the interpreter and resume it at some later 
point. You need to implement a custom monad for that, which can easily 
be done with the help of my  operational  package.

    http://projects.haskell.org/operational/

In particular, the examples

    WebSessionState.lhs
    TicTacToe.hs
    PoorMansConcurrency.hs

show how to suspend and resume the control flow. Feel free to request 
additional examples.


Best regards,
Heinrich Apfelmus

--
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