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Re: Unhealthy Haskell babel


From: Immanuel Litzroth
Subject: Re: Unhealthy Haskell babel
Date: Thu, 10 Dec 2020 19:40:02 +0100

Well another possible solution is to wrap the code blocks in
:{
xxx
:}
in
(defun org-babel-execute:haskell (body params) -- ob-haskell.el
Immanuel

On Thu, Dec 10, 2020 at 6:21 PM Lawrence Bottorff <borgauf@gmail.com> wrote:
>
> I see your point, i.e., compiled, multi-file projects are not really meant 
> for the REPL-dominant world of org-mode babel. Babel's sweet-spot would be 
> the interpreted world, the very best probably a Lisp language. Still, the 
> ability to add code to a running REPL should be possible. As I mentioned, SML 
> is a sibling of Haskell and its babel implementation worked fine for me as I 
> worked through an SML course. So yes, this appears to be a Haskell REPL 
> issue. I'm just a beginner with Haskell, and all my intro texts start you out 
> using the ghci REPL interactively. But then they switch you over to a text 
> file compiled in the REPL with :l myfile.hs . . . no explanation as to why 
> you can't just continue with the REPL putting the program in line-by-line. 
> The fact that I can use the :set +m to include multiple lines of code, but 
> cannot do a type definition is rather bizarre, though. This is a decision 
> Haskell made with their REPL and babel really can't do much about it, I 
> suppose. The Haskell .lhs literate option is interesting. Yes, I'd like to 
> see your tangle option, please.
>
> On Thu, Dec 10, 2020 at 4:28 AM Immanuel Litzroth 
> <immanuel.litzroth@gmail.com> wrote:
>>
>> I don't think org-babel is a good fit for compiled languages. If the
>> idea is to just take 1 snippet,
>> and "execute" that it means that to have a consistent whole you'd need
>> to put all the modules of
>> your program into that snippet (already impossible in Haskell, you can
>> have only 1 module per file),
>> compile that, run the resulting binary. Or org mode would have to have
>> some idea of what needs to
>> be retangled & rebuilt.
>> I think that using org-babel for compiled, multifile languages will
>> only work in very simple cases -- and
>> even then.. -- but will lead to problems very soon.
>> Immanuel
>>
>> On Thu, Dec 10, 2020 at 4:21 AM Lawrence Bottorff <borgauf@gmail.com> wrote:
>> >
>> > I'm looking into Haskell (latest ghci) again on org-mode. This
>> >
>> > #+begin_src haskell :results verbatim :exports both
>> > :set +m
>> > doubleSmallNumber x = if x > 100
>> >   then x
>> >   else x*2
>> > #+end_src
>> >
>> > works, but still the :set +m is necessary for it to see the whole. But this
>> >
>> > #+begin_src haskell :results verbatim :exports both
>> > :set +m
>> > factorial :: Int -> Int
>> > factorial 0 = 1
>> > factorial n = n * factorial (n - 1)
>> > #+end_src
>> >
>> > results in this on the REPL side:
>> >
>> > Prelude> :set +m
>> > factorial :: Int -> Int
>> > factorial 0 = 1
>> > factorial n = n * factorial (n - 1)
>> > "org-babel-haskell-eoe"
>> > Prelude>
>> > <interactive>:26:1-23: error:
>> >     • No instance for (Show (Int -> Int)) arising from a use of ‘print’
>> >         (maybe you haven't applied a function to enough arguments?)
>> >     • In a stmt of an interactive GHCi command: print it
>> > Prelude> Prelude> Prelude> "org-babel-haskell-eoe"
>> >
>> > which is the same behavior if I try to feed the program into the REPL one 
>> > line at a time, i.e.,
>> >
>> > Prelude> factorial :: Int -> Int
>> >
>> > <interactive>:40:1-23: error:
>> >     • No instance for (Show (Int -> Int)) arising from a use of ‘print’
>> >         (maybe you haven't applied a function to enough arguments?)
>> >     • In a stmt of an interactive GHCi command: print it
>> >
>> > So the :set +m trick (take multiple lines) doesn't help here. Obviously, 
>> > Haskell is not ready to be used with Babel. Can it be fixed? BTW, this 
>> > does work with the regular ghci REPL and haskell-mode. If it helps, 
>> > Standard ML, which has very similar syntax (it was Haskell's parent), 
>> > works fine.
>> >
>> > LB
>>
>>
>>
>> --
>> -- Researching the dual problem of finding the function that has a
>> given point as fixpoint.



-- 
-- Researching the dual problem of finding the function that has a
given point as fixpoint.



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