2 - Raspberry PI Community Projects

Figure 5.1
Use of a Provides field in order to not break dependencies
This feature is very useful, since it is never possible to anticipate the vagaries of development,
and it is necessary to be able to adjust to renaming, and other automatic replacement, of obsolete
software.
BACK TO BASICS
Perl, a programming
language
Perl (Practical Extraction and Report Language) is a very popular programming
language. It has many ready-to-use modules that cover a vast spectrum
of applications, and that are distributed by the CPAN (Comprehensive Perl
Archive Network) servers, an exhaustive network of Perl packages.
➨ http://www.perl.org/
➨ http://www.cpan.org/
Since it is an interpreted language, a program wrien in Perl does not require
compilation prior to execution. This is why they are called “Perl scripts”.
Current Limitations Virtual packages suffer from some troubling limitations, the most significant
of which being the absence of a version number. To return to the previous example,
a dependency such as Depends:libdigest-md5-perl (>=1.6), despite the presence of Perl 5.10,
will never be considered as satisfied by the packaging system — while in fact it most likely is
satisfied. Unaware of this, the package system chooses the least risky option, assuming that the
versions do not match.
GOING FURTHER
Virtual package versions
Although today virtual packages can't have versions, this will not necessarily
always be the case. Indeed, apt is already able to manage the versions of
Chapter 5 — Packaging System: Tools and Fundamental Principles
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