Proposal: add replay function to Control.Monad.Cont.Class

[Carter Schonwald]

This does sound more useful!
What are some simple expressivity examples for the two?

On Sun, Mar 7, 2021 at 1:36 PM Zemyla <zemyla at gmail.com> wrote:

> I kind of don't like it, because the continuation doesn't return anything
> but itself. I'd prefer something that works more like the setjmp function
> in C, taking a value and returning the value plus a function that lets it
> return the new value:
>
> setJump :: MonadCont m => a -> m (a -> m b, a)
> setJump a = callCC $ \k -> let
>   go b = k (go, b)
>   in pure (go, a)
>
> On Sun, Mar 7, 2021, 11:36 Carter Schonwald <carter.schonwald at gmail.com>
> wrote:
>
>> Yeah
>>
>> On Sun, Mar 7, 2021 at 12:16 PM Edward Kmett <ekmett at gmail.com> wrote:
>>
>>> I rather like label. +1 from me.
>>>
>>> On Sun, Mar 7, 2021 at 1:25 AM Tom Ellis <
>>> tom-lists-haskell-cafe-2017 at jaguarpaw.co.uk> wrote:
>>>
>>>> On Sun, Mar 07, 2021 at 03:25:16AM +0000, Alexandre Esteves wrote:
>>>> > replay :: MonadCont m => m (m a)
>>>> > replay = callCC $ pure . fix
>>>> >
>>>> > Using this in a do-notation block allows one to bind a name to the
>>>> > sub-block that starts immediately after.
>>>> > I reached for continuations to try to get this behavior for use with
>>>> > recursive flows without disrupting the reading of the main forward
>>>> flow and
>>>> > found how to do it in https://jsdw.me/posts/haskell-cont-monad/
>>>> under the
>>>> > name "goto".
>>>> >
>>>> > While "goto" is as familiar as a name can be, I feel "replay" more
>>>> > accurately conveys, that you can only 'go back', by stating what
>>>> actually
>>>> > is happening - that a sub-block we're currently evaluating is
>>>> replayed from
>>>> > its beginning.
>>>>
>>>> Looks like a "label" more than a "goto" to me.  Would "label" be a
>>>> good name?
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