[Haskell-cafe] Examples of Continuation monad that impossible to understand and maintain?

[Isaac Elliott]

I don't have any examples. Given that Cont essentially implements
unstructured control flow, I think that examples of `goto` misuse would
apply by analogy.

On Wed, 1 Sep 2021, 4:31 pm YueCompl via Haskell-Cafe, <
haskell-cafe at haskell.org> wrote:

> I can understand the purpose if it is advising against overusing surface
> syntax in CPS, but here the approach is to hide continuation beneath the
> beloved do notation on the surface, and monad laws plus possibly further
> laws to be added, will make it safer to program programs by end
> programmers.
>
> I do realize CPS is powerful yet dangerous (unsafe), abuse of CPS could be
> easy and quite unintentional, but what about abuse of "Continuation monad"?
>
> On 2021-08-31, at 22:46, Jeff Clites via Haskell-Cafe <
> haskell-cafe at haskell.org> wrote:
>
> Based on the preceding paragraph, I think that by “abuse” it means
> overuse, as in using CPS when you could have used straightforward code. I
> can imagine someone doing at the source code level the sort of things that
> would be done by a CPS-based compiler (converting everything possible to
> CPS), and ending up with a mess.
>
> For example, imagine you started with this code snippet:
>
>   let x = f a
>         y = g x
>   in h x y
>
> If you fully convert that to CPS you’d end up with 3 continuations (I
> think) and it would be much harder to understand. And adding an additional
> let binding later might involve a bunch of restructuring.
>
> I assume it just means that sort of thing. When someone first learns about
> continuations and their generality, it can be tempting to go overboard.
>
> Jeff
>
> On Aug 31, 2021, at 3:03 AM, YueCompl via Haskell-Cafe <
> haskell-cafe at haskell.org> wrote:
>
> Dear Cafe,
>
> I'm wrapping up my CPS codebase to provide some monadic interface, it
> appears almost the Cont monad, so the following statement is a pretty valid
> caveat to me now:
>
> > Abuse of the Continuation monad can produce code that is impossible to
> understand and maintain.
>
> Which can be viewed in context of Hackage at:
> https://hackage.haskell.org/package/mtl/docs/Control-Monad-Cont.html#:~:text=Abuse%20of%20the%20Continuation%20monad%20can%20produce%20code%20that%20is%20impossible%20to%20understand%20and%20maintain
>
>
> But I can't find concrete examples demonstrating the "impossible to
> understand and maintain" situation, in figuring out what pitfalls I'd
> rather to avoid.
>
> Please share what you know about it, many appreciations!
>
> Background of my CPS necessarity:
>
> Library code need to delegate STM transaction boundary delimitation to
> (scripting) application code, though `inlineSTM :: STM a -> m a` can be
> used to force some action to be within current tx, the usual `>>=` binding
> should honor whether a separate `atomically` tx should be issued for its
> rhs computation, as specified by the scripting context.
>
> Thanks,
> Compl
>
> _______________________________________________
> Haskell-Cafe mailing list
> To (un)subscribe, modify options or view archives go to:
> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
> Only members subscribed via the mailman list are allowed to post.
>
> _______________________________________________
> Haskell-Cafe mailing list
> To (un)subscribe, modify options or view archives go to:
> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
> Only members subscribed via the mailman list are allowed to post.
>
>
> _______________________________________________
> Haskell-Cafe mailing list
> To (un)subscribe, modify options or view archives go to:
> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
> Only members subscribed via the mailman list are allowed to post.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.haskell.org/pipermail/haskell-cafe/attachments/20210901/8e69f728/attachment.html>