in reply to Re^2: Pronoun Programming
in thread Pronoun Programming

I think a hash element reference would have to be a pointer to an HE struct. That contains pointers to both the key and it's value. The thing that is missing is some way to get back to the hash it is a part of, as they form a single linked list going in the wrong direction.

There are several ways I would like to extend Perl's hashes, had I the skills and patience. This is one. Another would be to add timestamps to keys, that gets set when keys are created. That would allow for time ordered hashes which could be useful. And the same field could be used to order keys according to any arbitrary sorting order, which would be more space and time efficient than current tied hash+array hybrid solutions.

But, as almost every attempt I've made at messing with Perl's internals has resulted in random, inexplicable crashes which my attempts to resolve have fallen on deaf ears and stoney ground, it's not something I am likely to get around to any time soon.

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.
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Re^4: Pronoun Programming
by plobsing (Friar) on Feb 05, 2008 at 14:32 UTC
    I tried implementing this out of curiousity. HE* DO have a pointer back to the original hash, but there's no guaranteeing that the hash is there any more.

    Thats why I tried using weakened references in stead. I would have used set/get magic if I was more comfortable with them, I never got those to work out for me before. Here's the begginings of the module (untested):
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        I was mistaken. Should have paid a little more attention while reviewing extending and embedding perl. $hash in the following structure refers to the hashed value of the key, not the hashtable from which the HE came. Confusing terminology. 
        # from Extending and Embedding Perl, section 4.5 
$HE = {
       NEXT => $HE_next,
       HEK => {
           HASH => $hash,
           LEN => length($key),
           KEY => $key,
          }
       VAL => $SV,
      };

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        My approach didn't try ordering, so the hash was actually based on a hashref, not an array.

        I looked over the tie modules on CPAN (the first 20 pages before I got bored). None of them seemed to implement the functionality of what I envisioned as a solution: A tied hash that gives defered processing objects as results.

        Being interested in something in inverse proportion to how useful that thing is, I expanded upon my ideas in the previous post. I think it caught feauture-use-itis though (2 tie classes and an overloaded inside-out class is a bit much complication for one module, IMHO).

        I called it Tie::LazyHash, but it probably would be better named Tie::DeferredLookupRefHash. But that's just ugly sounding.

        You can do a couple of things with the lookup values that invoke the actual lookup (which can be invoked multiple times for the same object): 
        $elem->delete;
$elem->exists;
$$elem = $x;
print $elem; # overloaded for convenience
print $$elem;

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