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All the Perl that's Practical to Extract and Report

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  • I'm not sure what you're complaint is, exactly. I think negative indices are pretty useful, but you seemed to only test them on empty arrays. They're useful on longer arrays because -3 means "start at the right and go back three; if you get to the left, give up." So, given @foo = (1, 2, 3), $foo[-3] is 1, $foo[-2] is 2, and $foo[-10] is undef.

    I would've thought that C would do something horrid like (type)*(array - index), but my C is lousy.
    --
    rjbs
    • I'm not complaining about negative arrays. I'm complaining that the behavior of arrays is inconsistent with regards to empty arrays and negative indices, specifically.
      • How is it inconsistent? Given @foo=(1,2,3); $foo[-10] does not exist. If fetched, it returns the "does not exist" value, which is undef. It's also C. It's not a valid lvalue, so it should throw an error.

        After all the -1 subscript is "first existing element from the right" not "a new element at the end." Or am I being thick?
        --
        rjbs
        • You're talking about reference. I'm talking about assignment, e.g.

          @foo = ();
          $foo[10] = "foo"; # legal
          $foo[-10] = "foo"; # illegal

          In the former case, index 10 does not exist. I create it and indices 0 to 9 now exist as undef. In the latter case, index -10 does not exist, but I cannot assign to it. Why not allow me to assign to a negative index on an empty array?

          • $foo[10] = "foo" is the same as (assuming an empty @foo), @foo = ( (undef) x 9, "foo", (undef) x 0)

            You want $foo[-10] = "foo" to be the same as @foo = ( (undef) x $m, "foo", (undef) x $n ), but what are $m and $n ? (On reflection, $m should probably be zero and $n be 9? What's the benefit of this behavior?)

            Does $foo[-10] = $bar[-5] = "foo" result in @foo being a different size than @bar ? (Based on our reflection above, they would be different sizes.)

            If @foo is already defined, then what happens when