It could mark a range as empty without actually filling in each bucket.

I just tried it. Setting element 10000 of an array takes 0.35 MB more RAM than setting element 0 on perl 5.8.8 for OS X on Intel. So, there's a cost, although not a large one.

In reply to Re^3: Could we save the memory occupied by "undef" in an array? by perrin
in thread Could we save the memory occupied by "undef" in an array? by lightoverhead

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