Re: [Caml-list] Opam use for teaching lab infrastructure

[Roberto Di Cosmo <roberto@dicosmo.org>]

Hi Fabien,
   we have been using opam last year in the advanced functional
programming course here at Paris Diderot, and we were confronted
to issues similar to yours.

Here are some lesson learnt:

On the student laptops
----------------------

The students *love* opam once they have it installed properly on their machines!
But getting opam up and running on a random laptop of a student can
be quite a challenge, though:

    - opam packages are not available/up to date for all distros

    - the opam binary installer is only available for 64-bit machines,
      so one may end up needing to recompile it, but there many things
      can go wrong: some machines do not have the proper development
      libraries/tools to compile OCaml/opam, and the students need help
      when they are left with a failed ./configure; some other students
      may install the OCaml package from the GNU/Linux distribution, then
      compile opam, and then start using opam with the OCaml installed
      globally, which can lead to great confusion when they start mixing
      up the ocamlfind from opam with the ocamlfind from the distribution.

    - My suggestion is to tell them clearly to compile opam, then perform
      an opam switch to (re)compile an opam-local version of OCaml, and then
      religiously stick to it, by putting the

              eval `opam config -env`

      in their bash/chs/whatever init script (opam does a pretty good job 
      to detect the running shell and exporting the right parameters).

      You may need to help them installing the necessary development environment
      (gcc, m4, devl libraries, etc.), I do not know how to avoid this on a
      random laptop :-(

On the machines in the lab
--------------------------
 
  Unfortunately, our students have a pretty low quota (you might wonder why,
  when Seagate is working on 5TB disks that will cost just a few hundred bucks,
  but that's another story), so we could not afford a local opam repo for each
  student.

  Instead, we just use a specific account where opam is installed locally, and
  then tell the students to use

             eval `opam config -env --root=/path/to/the/shared/.opam/dir`

  This way it's easy to add new libraries, visible to all the students, with
  no need to bother the sysadmin, but of course, they cannot play with different
  libraries by themselves.

  You will probably need to carefully set the rights on the shared .opam repo
  to make this work.

Hope this helps!

--
Roberto

On Thu, Sep 19, 2013 at 11:38:41AM +0200, Dagnat Fabien wrote:
> Hello,
> I'm teaching (basic) functional programming and (simple) compilation in ocaml
> (to master students). Currently, I ask the system administrators to install a
> basic ocaml package. I'm thinking on switching to opam to make it easier for
> students to experiment various libraries.
>  
> Does anyone has used opam for labs with student? I would be glad to hear any
> report on this mainly on the following points:
> - Is opam really usable when you keep changing of machine?
> - Having a .opam for all student accounts seem interesting so that they can
> freely experiment without interfering with others but has the cost of
> duplicating lot of common files. Any thoughts?
> - What is the usual size of an .opam directory? Mine is 1G but I don't know if
> it's usual.
> - What kind of ocaml libs do you introduce to the students? I was thinking of
> utop, ounit, core / batteries, menhir. 
> 
> Thanks in advance
> Fabien
> 
> 
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-- 
Roberto Di Cosmo
 
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