[Haskell-cafe] Asynchronous computations and error handling in the free monad

Will Yager will.yager at gmail.com
Wed Nov 9 22:10:53 UTC 2016

Without knowing exactly what the problem is, perhaps you could use "FreeT ast Either"?

This will allow you to extend the Free monad with failure semantics. 


> On Nov 9, 2016, at 15:34, Damian Nadales <damian.nadales at gmail.com> wrote:
> Yesterday I posted the following question to SO:
>    http://stackoverflow.com/questions/40495304/abstract-result-types-in-free-monads
> As discussion with Benjamin ensued, in which he stated that it is
> better to be explicit about the fact that we want parts of our code to
> run asynchronously. I am not so sure.
> I also have a similar question about how would you deal with fatal
> errors that could happen at the interpreter. I guess this could be
> modeled in the free monad by having a command returning a `Maybe` or
> `Either` type. However we're adding details about the interpreters in
> our DSL, since we are stating that certain command could cause fatal
> errors.
> So my question is what approach do you or would you use?
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