Shawn H Corey wrote:
On Fri, 4 Aug 2017 15:23:21 +0200
hw <h...@gc-24.de> wrote:
Now I´m confused as to what is a module and a package. Both are
files.
> [...]
This is very confusing so the convention is that one module has one
package. I'm telling you this because the terms module and package are
not interchangeable.
Indeed. I thought packages "have" modules because they are put into
files that are much like files modules are put into, and that modules
are modules and don´t have packages. In an case, I wouldn´t want to
split a module or a package into multiple files because the point of
having them is having stuff in one file (which then can be used).
To summarize:
* A module is a file with the extension *.pm
* A module may have zero, one or many packages but please stick to one
package per module.
You mean it´s the wrong way round because a module is like module.h and
a package is like package.c, with the module.h being #included and the
package.c being compiled and linked, but perl #includes the package.c
and compiles and links the module.h instead?
Basically, I wouldn´t find anything wrong with a package that uses
modules.
* Packages may be distributed among many files but please stick to one
module for each package.
* A package may be a class. If it has the keyword `bless`in it, it is a
class.
What happens when you bless something in a module?
The way I would do it would be to separate out what is common in
both Foo and Bar and put them in a separate module. Then Foo and
Bar can `use` it as their parent.
I think that might be the best solution. I could make a metaclass
that contains the methods common to both FOO and BAR and have both of
them descend from it.
However, that feels like using inheritance in an upside down manner.
But perhaps it´s supposed to be used like that?
Yes, they are called virtual classes. Aka generics in Java and
interfaces in general.
http://www.cs.utah.edu/~germain/PPS/Topics/interfaces.html
Interfaces? Hm.
Well, ok, I could think of the problem I´m facing as an interface
problem. I need to be able to ask FOO and BAR about quantites, and
how each of them answers the question depends on them because each
requires a different method to generate an answer. The interface,
i. e. how to ask them, can be the same for both.
How do I implement interfaces in perl?
BTW, why are classes based on upside-down inheritance called virtual
classes? They´re as real as others.
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