Re: [O] ocaml babel no longer works?

[Eric Schulte]

Alan Schmitt <address@hidden> writes:

> Hello,
>
> Eric Schulte writes:
>
>> Thanks for looking into this.  I've applied a patch to ob-ocaml.el which
>> should handle the two different tuareg execution functions.
>
> Thanks a lot.
>
> About the thing "getting stuck", I made some progress. My error was that
> I did not add ";;" at the end of my ocaml phrase, which resulted in an
> error in the toplevel:
>
> #+begin_quote
>         Objective Caml version 3.12.1
>
> # let x = 2 in x
> "org-babel-ocaml-eoe";;
>   Characters 13-14:
>   let x = 2 in x
>                ^
> Error: This expression is not a function; it cannot be applied
> #+end_quote
>
> As you see, it's trying to apply the 'x' to the "oeo" thing. My guess is
> that babel waits until seeing this special string before sending the
> result back. By the way, this allows for some fun things, like this:
>
> #+BEGIN_SRC ocaml
> let f x = () in f
> #+END_SRC
>
> make babel stuck because the interpreter is in this state:
>
> #+begin_quote
> # let f x = () in f
> "org-babel-ocaml-eoe";;
>   - : unit = ()
> #+end_quote
>
> So I have a suggestion and two feature requests.
>
> The suggestion: instead of appending '"org-babel-ocaml-eoe";;' to the
> code, how simply put ';;' (which will make sure everything is flushed)
> then detect the toplevel is done by seeing the string '# ' at the
> beginning of the line? Would there be an issue with the fact that this
> line does not have a newline? If so, an alternative suggestion would be
> to use the longer ';; "org-babel-ocaml-eoe";;' which makes sure the
> phrase in the input won't interact with the marker.
>

You can customize the `org-babel-ocaml-eoe-output' and
`org-babel-ocaml-eoe-indicator' variables so that they match the above.
If this proves generally useful then I'd be happy to admit this change
to the core.

>
> The first feature requests: if there is an error, could it be parsed?
> (It probably always start with 'Error: '). Then the error could be put
> in the result block, instead of waiting for the marker that will never
> appear.
>

In `org-babel-execute:ocaml' first the `raw' variable is assigned to the
raw output of the ocaml session, it is then parsed into the `clean'
variable.  Between these two steps it should be possible to check for an
error string and possibly raise an error with
`org-babel-eval-error-notify'.

>
> The second feature request: I want to use this for my ocaml lab classes
> (I'm thinking of giving them an org file they have to complete by
> writing the caml code). Could it be possible to have an option for the
> full output of the compiler (and not just the result) to be printed? I
> see it does it when it does not recognize the type of the output. So I
> guess such an option would be applied to either
> org-babel-ocaml-parse-output or the place where it's called.
>

I would think adding a ":results verbatim" header argument would
suffice, but perhaps this is not the case.

>
> Thanks a lot for any suggestion as how to implement this. I think I see
> how to do the second one (except I don't know how to add a configuration
> variable to toggle it). I have no idea about the first one, though.
>

I hope these pointers are useful.  I apologize for not being able to
take a look at this myself, but I'm simply too busy.  ob-ocaml could
certainly use some attention, and I hope that if you do make
improvements you consider contributing them back to Org-mode.  In
general other more mature language modes should serve as a guide to most
implementation questions.

Cheers,

>
> Alan

-- 
Eric Schulte
http://cs.unm.edu/~eschulte