in reply to Re^2: Producing 2 lists from a grep call
in thread Producing 2 lists from a grep call

I quite like that one. I came close to that but missed (actually, simply wasn't aware of) the @{\@array) 'trick'.

However (you knew that was coming right?), as I can do: 

my (@a1,@a2) = ([1,2,3],[3,2,1]);

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Update: the above line doesn't work after all

I had tried: 

my (@a1,@a2) = ([1,2,3,4,5,6,7],[7,6,5,4,3,2,1]);
print Dumper(@a1), Dumper(@a2);

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which gave:

$VAR1 = [
          1,
          2,
          3,
          4,
          5,
          6,
          7
        ];
$VAR2 = [
          7,
          6,
          5,
          4,
          3,
          2,
          1
        ];

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which certainly lookedlike it had worked! It was only after seeing this that I went back and added a couple of labels

print "a1\n", Dumper(@a1), "a2\n", Dumper(@a2);

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That I saw what tstock meant below.

Thanks tstock, I'll be more careful in future with my quick tests. (I agree about the loop/if being better too.)

end of update

Which personally I find a very clear yet concise way of declaring and initialising two arrays. It still seems as if something close to: 

my ( @dirs, @files)= 
   ( @{-d}, @{-f} ) for (readdir DIR);

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could be possible if I could only get the syntactic sugar right!

This is only an exercise in my trying to understand arrays and list contexts etc. ie. Its essentially a purely academic excercise for late (for me) on a Sunday evening, and so not worthy of anyone's time unless they are also in play mode.

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Re: Re: Re: Re: Producing 2 lists from a grep call
by tstock (Curate) on Jun 16, 2002 at 23:40 UTC
    However (you knew that was coming right?), as I can do:
    my (@a1,@a2) = ([1,2,3],[3,2,1]);

    This doesn't work, sorry. You get @a1 with two array references and @a2 undefined.

    tstock

    Update : This is your one liner: (someone please -- me down for posting this) 
    map {
     ($_ ne '.') && ($_ ne '..') &&
     push @{ -d "$base/$_" ? \@dirs : \@files }, $_
} (readdir DIR);

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    I think we can agree that the FOR LOOP/IF STATEMENT is probably a nicer solution ? :)
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      I think we can agree that the FOR LOOP/IF STATEMENT is probably a nicer solution ? :)
      Especially since it's almost the for loop I posted - just s/map/for/, pull the (readdir DIR) up top, slip a next into the loop, and there you have it.

      If you actually want something that's not a for loop in disguise, you could pull a really horrible trick like 
      my @dir;
my @files = map {
    ($_ ne '.') && ($_ ne '..') &&
    -d "$base/$_" ?
        do { push @dir, $_; () } :
        -f "$base/$_" && $_
} readdir DIR;

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      But if the Communications Decency Act had gone through I wouldn't have been able to even post this.

      Makeshifts last the longest.

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