[Haskell-cafe] Zoom instance for Coroutine

Mario Blažević blamario at ciktel.net
Mon Mar 14 22:34:43 UTC 2016

On 03/11/2016 02:35 AM, Konstantin Saveljev wrote:
> Hello,
> I am using monad-coroutine 
> <https://hackage.haskell.org/package/monad-coroutine> package and have 
> something like Coroutine (Await Int) (State MyState) Int (simplified 
> version, for example purpose).
> MyState is deeply nested and I do a lot of modifications in it. 
> Previously (with different data types) I was able to use zoom from 
> lens <https://hackage.haskell.org/package/lens>in order to simplify 
> the typing/view of code which operates on some subtree of the state, e.g.:
> |zoom (company.assets) $ dosomething.a = someComputation anotherthing.b 
> = False this.that = "someString" |
> The problem I am having is that I cannot come up with instance 
> Zoom for the Coroutine and was wondering if anyone is able to help me 
> with that?

     I don't know if it gets you instance Zoom, but you can combine zoom 
with mapMonad to dive into a field of your state.


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