Sophie: ocaml-findlib-devel-1.2.4-5mdv2010.1 x86

ocaml-findlib-devel-1.2.4-5mdv2010.1.x86_64.rpm

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>Glue code</A
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><P
>Imagine we have two packages p and q that are normally
independent, i.e. one can link p without q, and q without p. However,
when both p and q are used in the same program, it is expected that
they cooperate with each other. Of course, this situation can be
modeled with the help of subpackages (a real-world example of this are
p=lablgtk and q=lablgl).</P
><P
>The idea is as follows: p has a subpackage p.for_q that contains
code with special features for q, and q has a subpackage q.use_p that
depends on p, p.for_q, and q, and that contains the code using the 
special features of p. Expressed in META files, p would define

<PRE
CLASS="PROGRAMLISTING"
># META file for p:
requires = "..."
archive = "..."

package "for_q" (
  requires = "p"
  archive = "..."
)</PRE
>

and q would define

<PRE
CLASS="PROGRAMLISTING"
># META file for q:
requires = "..."
archive = "..."

package "use_p" (
  requires = "q,p.for_q"
  archive = "..."
)</PRE
>

Of couse, the program using both libraries must explicitly enable
the subpackages by mentioning "q.use_p" on the ocamlfind command line,
otherwise the glue code would be omitted.</P
><P
>Unfortunately, it is not possible to use the package predicates
pkg_p and pkg_q to add archives depending on whether the other
package is also selected. The problem is that the order cannot
be specified, i.e. whether p must be linked first or q.</P
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