Re: "Missing" libraries/concepts found in other languages/ecosystems?

["Linus Björnstam" <linus.internet@fastmail.se>]

On Sat, 11 Jul 2020, at 02:34, Zelphir Kaltstahl wrote:
> The comments about exception handling also reminded me of the following
> blog post:
> 
> https://blog.sulami.xyz/posts/common-lisp-restarts/
> 
> Pretty cool concept as well.
> 
> If there anything like it in Guile or is something like it possible
> (probably, right?)?

I implemented a restart system in top of call/cc back in 2012, but that was slow and had some interesting (as in completely wrong) edge cases. 

Doing it with delimited continuations should be fast and a lot simpler. Someone took my code and made it useful for chez, and then I saw something that looked vaguely similar in one of the r7rs-large dockets. 

Anyway, it is possible and probably not more than 100loc to do it properly using continuations.
> 
> 
> On 7/11/20 2:19 AM, Zelphir Kaltstahl wrote:
> > Hi all!
> >
> > On 7/10/20 1:20 PM, Catonano wrote:
> >> Il giorno ven 10 lug 2020 alle ore 12:21 Chris Vine <vine35792468@gmail.com>
> >> ha scritto:
> >>
> >>> On Fri, 10 Jul 2020 10:49:37 +0200
> >>> Catonano <catonano@gmail.com> wrote:
> >>>> Il giorno mer 8 lug 2020 alle ore 20:22 Zelphir Kaltstahl <
> >>>> zelphirkaltstahl@gmail.com> ha scritto:
> >>>>
> >>>>> Hi Simen!
> >>>>>
> >>>>> On 7/8/20 6:00 PM, guile-user-request@gnu.org wrote:
> >>>>>> Hi, I'm new to scheme/lisp, so I'm trying to find out how to do
> >>>>>> things the "lisp
> >>>>>> way". On the other hand, I like things from other ecosystems too,
> >>>>>> and I'm having
> >>>>>> problems finding this for Guile. It might be because there's no
> >>>>>> need for it/I'm
> >>>>>> terrible at searching/nobody had the time yet, or something else.
> >>>>>>
> >>>>>> I've been trying to find implementations for https://reactivex.io
> >>>>>> without any
> >>>>>> luck. And I'm unable to find implementation of FP concepts as
> >>>>>> found in Haskell
> >>>>>> and other languages. Functor, Monad, lenses (and other helpers for
> >>>>>> working with
> >>>>>> immutable data).
> >>>>>>
> >>>>>> Does things like this exists, or is it better to use something
> >>>>>> else?
> >>>>>>
> >>>>>> Regards Simen
> >>>>> To what others already have written I will add:
> >>>>>
> >>>>> From time to time one can copy ideas from Racket or look at what exists
> >>>>> in Racket for solving a problem or seeing what the approach is.
> >>>>>
> >>>>> Catonano identified already the lack of examples in the Guile guide. I
> >>>>> fight with that myself, so I created a repository with examples.
> >>> Perhaps
> >>>>> I should somehow add them to the guide. I've not looked into how to do
> >>>>> that. Probably some commit in a repo somewhere for the guide:
> >>>>>
> >>>>> https://notabug.org/ZelphirKaltstahl/guile-examples
> >>>>>
> >>>>> Hope this can help!
> >>>>>
> >>>> Thank you, yes that helps
> >>>>
> >>>> In fact, it's a precious resource !
> >>>>
> >>>> I was especially delighted with the examples of using exceptions !
> >>>>
> >>>> I had so missed examples of those !
> >>>>
> >>>> As for the manual, very recently a mention of Guile Hall ended up being
> >>>> included in the manual
> >>>>
> >>>> The same could be done with your examples collection
> >>>>
> >>>> I also think that your collection could be mentioned by the Guile web
> >>> site,
> >>>> maybe in the "learn" section
> >>>>
> >>>> Here's the repo for the web site:
> >>>> https://git.savannah.gnu.org/cgit/guile/guile-web.git/
> >>>>
> >>>> a regular patch could do
> >>>>
> >>>> What do people think of mentioning this resource on the Guile web site ?
> >>> Whilst I don't have strong feelings, as a general approach I think it is
> >>> better to include additional examples (where needed) in the body of the
> >>> manual, which I think is generally well written.
> >>>
> >> As long as some examples are reachable from an officially sanctioned
> >> documentation source, I'm ok with that
> >>
> >> What I find problematic is the casualness in referring to bits scattered
> >> all around
> >>
> >> The web site was just an idea, the manual would be perfectly fine
> >>
> >> Also, at this level of detail what some find helpful others don't.  You
> >>> were delighted above with the exceptions example, whereas (if I read
> >>> the right one) I thought that that was one of the weaker ones.  It
> >>> concentrates on R6RS/R7RS exceptions and with-exception-handler rather
> >>> than with guile's much easier to use catch expression (for guile-2.2)
> >>> or (for guile-3.0) its beefed-up with-exception-handler and exception
> >>> objects.
> >>>
> >> Ah there has been a misunderstanding here
> >>
> >> I was convinced that the exceptions example was of the last layout for
> >> using exceptions reached recently in Guile 3.x
> >>
> >> If it's not, I agree it's less valuable
> >>
> >> But I think the author was just confused or led astray by the casualness of
> >> referring to scattered bits, I'm not blaming them
> >>
> >> I'd be grateful if anyone with enough understanding of the issue would
> >> contribute a proper example of how to use exceptions according to the last
> >> exceptions reorganization in Guile 3.x
> >>
> >> I would be happy to send a patch for the manual containing such example and
> >> a few words, as I did with the mention of Guile Hall
> >>
> >>
> >> with-exception-handler is a tricky beast and the example didn't deal
> >>> with the main case: most uses of exceptions involve handling them and
> >>> moving on with program execution from the point where the exception is
> >>> caught, and to do that using with-exception-handler instead of
> >>> guile's 'catch' form you have to have a call/ec helper (or with
> >>> guile-3.0 you can just set the #unwind argument to true).  Instead you
> >>> are left with the idea that you use continuable exceptions for that
> >>> (which while they do stop the program exiting are something different)
> >>> or the R6RS/R7RS guard form.
> >>>
> >> I'm not following you on this because I don't know enough of both the Guile
> >> new idea of how to use exceptions and the R6/7RS one
> >>
> >>
> >>> I am not trying to be critical here - I think examples are useful to
> >>> convey points and some of them were fine.  My point is more about venue.
> >>>
> >>  No, that's ok, that's why I asked
> >>
> >> In fact, should we end up with a proper example in the manual, that would
> >> be a positive outcome
> >>
> >> I'd say more, here
> >>
> >> I'd go systematically through all the examples in that repo and do a
> >> similar assessment if we can add it to the manual as is or if it needs
> >> refinement
> >>
> >> I can't do this on my own because in many cases I don't know enough to come
> >> up with valid examples myself
> >>
> >> But I'd be happy to prepare patches for the manual, given the right
> >> directions
> >
> > I would be glad, if any non-optimal example was extended or updated by a
> > more knowledgeable person or I was told what I could improve in some
> > example. The examples in the repository are only, what I was able to
> > understand and I often find myself looking up, how to do something again.
> >
> > If anyone wants to take any example and put it in the docs, go ahead.
> > Only don't think that my examples are the last word on how to do things.
> > Far from it!
> >
> > About the exceptions thing: Aha! I should look into that again. I
> > thought the "conditions" thing was already pretty cool and useful. Once
> > an exception happens, you can react on it. I did not understand the
> > "call/ec helper" part, but perhaps I can understand it, when I check the
> > docs for the new exceptions in Guile 3.
> >
> > I had another thought: Why do we not create this kind of so called
> > "awesome list" for Guile? There were some links in this discussion,
> > which might be a good fit on such a list and it is kind of informal,
> > easy to extend. Whenever someone asks for pointers, we could also
> > mention that list and perhaps they can find cool things in it. They
> > could see, that Guile is viable, because there are so many things people
> > do with Guile, or they could see their use case covered already.
> >
> > Best regards,
> > Zelphir
> >
> >
> 
>