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Re: Re: Use modules or roll your own?

by ichimunki (Priest)
on Jul 29, 2002 at 15:27 UTC ( #186009=note: print w/ replies, xml ) Need Help??


in reply to Re: Use modules or roll your own?
in thread Use modules or roll your own?

The problem there isn't a "pointless use of OO", but rather an API that isn't very sensible. One is tempted to ask why the module has an interface that forces a user to create an instance, give the instance a number, and then retrieve a string from the instance when a simple class method exported would have worked more easily. I mean, then I have to remember whether the current number in the instance is the one I want-- which is the sort of "internal state of object" knowledge the rest of my program shouldn't have to be thinking about. It would bother me a lot less if the module had fewer steps:

use Lingua::EN::Numbers; my $n = Lingua::EN::Numbers->new; print $n->get_string(1281), " fish in the sea.\n"; #or use Lingua::EN::Numbers qw(get_string); print get_string(1281), " fish in the sea.\n";
With this sort of interface I have a choice of whether or not to pollute my namespace with a function name (like with CGI.pm, I prefer not to attempt to export all those HTML markup tags as function names).


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Re: Use modules or roll your own?
by Abigail-II (Bishop) on Jul 29, 2002 at 15:33 UTC
    One is tempted to ask why the module has an interface that forces a user to create an instance, give the instance a number, and then retrieve a string from the instance when a simple class method exported would have worked more easily. I mean, then I have to remember whether the current number in the instance is the one I want-- which is the sort of "internal state of object" knowledge the rest of my program shouldn't have to be thinking about.

    This is exactly what I mean by "pointless OO". Even your suggested class method is "pointless OO" to me. It doesn't buy you anything, except additional clutter.

    Abigail

      For a module with one essential function, parsing a number into an English string, it does seem excessive. But what if my program already has a get_string() function or an %N hash, and I add this module after the fact? The OO layer protects me from name collisions (and in my example is completely optional). While I might not worry too much about it for Lingua::EN::Numbers, I certainly would worry if CGI didn't offer me a choice-- that module has the potential to export several dozen function names, many of which (in a CGI script) might clash with my function names (poorly chosen names, perhaps).

      The OO isn't really pointless. It's happening either way-- exporting symbols without being asked to do so is just a sneaky way of concealing it is all. What I've said is that it should be explicit and optional for a module where the instance is really just an instantiation of a machine, rather than an instance of a class with unique properties that would distinguish it from other instances in the same class.

      Essentially the instance becomes a shorter way of doing print Lingua::EN::Numbers->get_string(1281), " fish in the seas\n";... which you can also get around by offering the ability to export get_string(). Is there an actual reason for avoiding instantiation of a machine to prevent namespace collision? Or is the objection purely aesthetic?

        But what if my program already has a get_string() function or an %N hash, and I add this module after the fact?
        Well, so what? You _do_ know the working of Perl, don't you? Then you _do_ know that if you do:
        use Module ();
        the import() routine isn't called, and nothing will be exported. In which case, you can still use the function by calling it like:
        Module::get_string ()
        But a name clash is an exceptional case - normally you don't have a name clash (I've been programming Perl for over 6 years now, I cannot recall ever having had a name clash problem), and you can just use the short get_string. But with a class method, you have to use Module -> sub, even if it's not necessary.
        The OO isn't really pointless. It's happening either way-- exporting symbols without being asked to do so is just a sneaky way of concealing it is all.
        Exporting symbols without being asked is only a sneaky way if there isn't an easy way to avoid it. All you need to do is ask to _not_ import anything. That takes a whopping two characters. A module author using Exporter gives the programmer a choice - a module author using OO to avoid name clashes doesn't. I know who acts Perlish, and it ain't the latter programmer.

        As for the %N of Lingua::EN::Numbers::Easy, let me quote from the manual:

               By default, "Lingua::EN::Numbers::Easy" exports a hash
               "%N" to the importing package. Also, by default, "Lin-
               gua::EN::Numbers::Easy" uses the British mode of "Lin-
               gua::EN::Numbers". Both defaults can be changed by
               optional arguments to the "use Lingua::EN::Numbers::Easy;"
               statement.
           
               The first argument determines the parsing mode of "Lin-
               gua::EN::Numbers".  Currently, "Lingua::EN::Numbers" sup-
               ports British and American.  The second argument deter-
               mines the name of the hash in the importing package.
        
                   use Lingua::EN::Numbers::Easy qw /American %nums/;
            
               would use American parsing mode, and "%nums" as the tied
               hash.
        
        If %N gives you a name clash, just use any other suitable name. OO isn't the only way of solving name clash problems!

        Abigail

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