in reply to Trying to get fancy...

*blink* *blinkblink*

Wow. That takes my vote for most obfuscated-but-didn't-mean-to code of the day.

First, a rewrite of the code, so we can start to see what's going on: 

$listA[0] = [qw(1 foo bar)];
$listB[0] = [qw(1 bar baz)];

print "First record from \@listA: $listA[0][0]\n";

@listToExpire = grep { } @listB;

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The {} say that you need to do some stuff on each element of @listB. However, your code is of the form grep ( @listB ); Are you sure this is what you want?

Update: Try the following: 

my @listToExpire = grep { my $a = $_; (grep /$a/, @listA) ? () : ($a);
+ } @listB;

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Interestingly enough, you can substitute map for the grep. Of course, I wrote it initially with map, cause that's how I think. TMTOWTDI.

------
We are the carpenters and bricklayers of the Information Age.

Don't go borrowing trouble. For programmers, this means Worry only about what you need to implement.

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Re: Re: Trying to get fancy...
by Purdy (Hermit) on Nov 28, 2001 at 20:36 UTC
    Yep - for each element in @listB, I want to pry out the first element, assign it to $b and then do another nested grep on all elements of @listA and see if $b is in there. If it isn't, then I want it assigned to the overall @listToExpire array.

    I rewrote the line to use the { }'s: 

    @listToExpire = grep { $b = (@{$_})[0] &&
 grep { $a = (@{$_})[0] && $b != $a } @listA
 } @listB;

    [download]

    Still the same result:
    Use of uninitialized value in numeric ne (!=) at ./listMgr.pl line 62.
    Use of uninitialized value in numeric ne (!=) at ./listMgr.pl line 62.

    I know I could do it in a more readable foreach loop (or a lookup hash), but thought I would take on a challenge, instead. :)

    Jason

    Update: I got it to work! Thanks, dragonchild! Here's the final version: 

    @listToExpire = grep { $b = (@{$_})[0]; grep { $a = (@{$_})[0]; $b != 
+$a } @listA } @listB;

    [download]

    It was those '&&''s ... I still don't understand them outside of the typical boolean EXPR. Need to grok that & the 'and|or' stuff, too.

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[d/l]
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      Though readability may not be a high priority for you in this excercise, consider changing this:

      (@{$_})[0]

      to this

       $_->[0]
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        *laugh* ... thanks. Lord help whomever adopts my code whenever that happens. Fortunately, this exercise is for a temporary utility script, but with my success, I will prolly adopt it more often. Hermmmm...

        Jason

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        If I could have voted this up twice, I would have. :)
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