Virtual packages in findlib

Virtual packages in findlib

[Dario Teixeira]

Hi,

(This is somewhat related to my previous question; having an order-preserving
Ocamlbuild would be moot if findlib supported some sort of virtual packages).

Suppose that for successful linking you need a package B to appear after
package A1.  However, A1 is only one particular instantiation of A-ness.
You could replace A1 with A2 or A3, and the program would also link and run.

Is there a way of expressing this sort of dependency with findlib?  Something
like "requires = A1 | A2 | A3".  Or even better, allowing packages A1, A2,
and A3 to provide a virtual package "A", and make B depend on that.  (The
Debian folks will recognise this pattern).

Best regards,
Dario Teixeira

Re: [Caml-list] Virtual packages in findlib

[Stefano Zacchiroli]

On Tue, Jul 07, 2009 at 11:07:55AM -0700, Dario Teixeira wrote:
> having an order-preserving Ocamlbuild would be moot if findlib
> supported some sort of virtual packages).

Can you explain that? I don't see why virtual packages can resolve
ordering problems.

(Following your analogy, the same problems exist with Debian packages:
if you have pre-dependencies which force an order among packages, you
cannot fix that by resorting to virtual packages.)

Cheers.

-- 
Stefano Zacchiroli -o- PhD in Computer Science \ PostDoc @ Univ. Paris 7
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