Re: Unhealthy Haskell babel

[Immanuel Litzroth]

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.