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Re: Overloading Perl's Built-In's

by dchetlin (Friar)
on Jan 12, 2001 at 13:57 UTC ( #51333=note: print w/replies, xml ) Need Help??

in reply to Overloading Perl's Built-In's

This is an excellent and well thought out question. Solid ++. The answer is, you haven't done anything wrong. The documentation is a little unclear on this point, but certain Perl operators are overridable, and certain others aren't. In perl 5.6.0 and earlier, chomp was not overridable. So nothing you can do will get your subroutine to be called in place of the built-in.

However, our very own ctweten noticed this in September and discovered that there's no reason at all chomp (and chop) shouldn't be overridable, and patched perl to make that possible. This change was too late for 5.6.0, but is in 5.7.0 and has been integrated into the 5.6.1 trial release 1. So, pending something horrifically bizarre, your first test module should work just fine on 5.6.1.

In the meantime, I would suggest playing around with a different operator to learn how to overload built-ins. If you're interested and have a copy of the source for your version of perl sitting around, the way to figure out what's overridable is by this one-liner, courtesy Nick Ing-Simmons:

perl -ne 'print "$1\n" if /return\s*KEY_(\w+)/' toke.c

Hope this is helpful. Keep up the good work.


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Patched Perl and toke.c
by bbfu (Curate) on Jan 12, 2001 at 14:11 UTC

    Thanks for your help! I'm definately going to have to look at toke.c when I get the chance (tomorrow at work =).

    Is Perl 5.7 out already? I knew about 5.6 and I thought they were working on 5.6.2... Did they skip over 5.6.2 and are comming back to it after 5.7? Maybe I should start reading Perl News, too! =) And I only just found this site!

      Is Perl 5.7 out already
      • 5.7 is the development branch that will eventually produce 5.8.

      • 5.6.x is the maintenance and bugfix branch for 5.6.

      "Perl makes the fun jobs fun
      and the boring jobs bearable" - me

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[Lady_Aleena]: My biggest problem with hashes at the moment is one with 2,501 keys.
[choroba]: how many event types are there?
[Corion]: Also I found that I can't conveniently weaken an array slot, which also is inconvenient, as I want my one-shots to disappear if the caller discards them
[Corion]: choroba: Currently two or three that my program handles (WWW::Mechanize:: Chrome), but there might be more that become interesting
[Corion]: But I don't expect more than 100 to be active at the same time, so I'm not really sure if there is a not-too-fancy data structure that is maintained with few lines of code where the performance is better than the linear scan ;)
[Corion]: But I should do a mock-up program so that others can see what I'm talking about ;)
[robby_dobby]: Corion: I hope you know all too well that passing around "fancy" datastructures is a recipe for disaster :-)
[robby_dobby]: As in, it's-too-fancy- that-it-will-be- messy-to-handle
[choroba]: bit vectors as keys?
[robby_dobby]: Hmm, I keep falling asleep at my desk, while maintaining an active appearance. Am I getting old?

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