in reply to XS ReadOnly HVs

This is a very good question, and has been raised on p5p in the past. As far as I know (which might not be far enough - I'm doing more category theory than programming these days) there is still no simple way to do what you want.

The most concerted attempt to change this was made by Jeff Friedl in 2001. Take a look at the threads starting here, here and here. As you can see, the necessary code has all been written, but doesn't seem to have been incorporated into perl. You could try asking p5p about the status of this.

Update: On closer inspection, it seems that this has been incorporated into Perl 5.8. Look at the module Hash::Util. It seems that, in Perl 5.8, the SvREADONLY flag does prevent new keys from being added to a hash. What version of Perl are you using?


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Re: Re: XS ReadOnly HVs
by Anonymous Monk on Apr 03, 2003 at 18:29 UTC

    Thanks a lot for pointing me in the right direction...
    I am currently using 5.6.1 but will most certainly upgrade to 5.8.x.

    So the only way of enforcing that behavior for hashes will be to require 5.8.0; in my modules?
    That will prevent users with older perl from using it...

    Any thoughts?

      Yes, I think you're right. On the other hand, you haven't explained why you rejected the low-tech alternative of using a tied hash. If it was for speed reasons, and compatibility is important to you, you could fall back to a tied hash implementation on older perls.

      Then at least it would work on 5.6.1, albeit slightly more slowly.


        Good thought... I'll look into that when I get there.