Help resolve Useless use of array element in void context warning.

talk2kvj has asked for the wisdom of the Perl Monks concerning the following question:

Here is a small piece of code that i couldn't understand. and i get an error as indicated in the comment below. can anyone please explain me the reason for this and what that particular line is doing.

thanks in advance.

foreach $item (@results) {
@line=split/,/, $item;
$seen{$line[1]}="0";
#$seen{$item}=0;
#print "LINE 1 $line[1]\n";
}
foreach $item (@results) {
@line=split/,/, $item;
if ($line[0] =~ /1|6|7|8|9|5/) {
&integrate;
sub integrate {
%matching=();
if ($line[0]=~/6|7|8|/) {
$overlapc=$line[1];
    foreach $itemi (@eresults) {
    @linei=split/,/, $itemi;
        if ($linei[1] eq $line[1]) {
        @matchone=split/ /, $linei[2];
        $lengthandn=$line[4].',', $line[5]; ##error here--- Useless us
+e of array element in void context--can u please tell me what this li
+ne does.
        $matching{$matchone[0]}="$lengthandn";
        $matching{$matchone[1]}="$lengthandn";
        #$seenclone{$matchclone[1]}="1";
#print  "678 line 1 $line[1] Length $lengthandn matchclone $matchclone
+[1] m0 $matchclone[0]\n";
        }
    }
[download]

20040527 Edit by castaway: Changed title from 'newbie- help with a piece of code'

Comment on Help resolve Useless use of array element in void context warning. Download Code

Replies are listed 'Best First'.
Re: Help resolve Useless use of array element in void context warning. by Zaxo (Archbishop) on May 26, 2004 at 19:57 UTC
You have comma where I think you want dot, `# $lengthandn=$line[4].',', $line[5]; # ^ $lengthandn = $line[4] . ',' . $line[5];` [download] After Compline, Zaxo	[reply] [d/l]
Re: Re: Help resolve Useless use of array element in void context warning. by talk2kvj (Novice) on May 26, 2004 at 20:06 UTC
Thank you all for the help. It worked. `http://www.perlmonks.org/index.pl?node_id=366807` [download]	[reply] [d/l]
Re: Help resolve Useless use of array element in void context warning. by BrowserUk (Patriarch) on May 26, 2004 at 19:55 UTC
It looks like the line is trying to concatenate the 4th and 5th elements of the line together separated by a comma, but the second dot operator has been typod as a comma. `$lengthandn=$line[4].',',$line[5]; # ^ should be .` [download] That line would probably be better written as `$lengthandn = "$line[4],$line[5]";` [download] Examine what is said, not who speaks. "Efficiency is intelligent laziness." -David Dunham "Think for yourself!" - Abigail	[reply] [d/l] [select]
Re: Help resolve Useless use of array element in void context warning. by pbeckingham (Parson) on May 26, 2004 at 20:05 UTC
Take that line out from the code, and it looks like: `$lengthandn = $line[4] . ',', $line[5];` [download] I suspect that the last comma on the line was intended to be a period, which eliminates the error, and is probably what you wanted, leaving: `$lengthandn = $line[4] . ',' . $line[5];` [download] Update: Oops - didn't see the earlier of the duplicated posts with answers already provided.	[reply] [d/l] [select]
Re: Help resolve Useless use of array element in void context warning. by Trag (Monk) on May 26, 2004 at 19:54 UTC
I'm new enough that I don't know either, (if I had to guess, it's treating a normal variable as an array, i.e `my $foo=1; print $foo[5];` will not work, I think (UPDATE: Having read the other posts, it looks like I'm wrong about that)). For future reference, please place your code between <'code'> <'/code'> in posts like these (minus the quotation marks though). It makes it much easier to read. Here's a cleaned up version of your code: `foreach $item (@results) { @line=split/,/, $item; $seen{$line[1]}="0"; #$seen{$item}=0; #print "LINE 1 $line[1]\n"; } foreach $item (@results) { @line=split/,/, $item; if ($line[0] =~ /1\|6\|7\|8\|9\|5/) { &integrate; sub integrate { %matching +=(); if ($line[0]=~/6\|7\|8\|/) { $overlapc=$line1; foreach $itemi (@eresults) { @linei=split/,/, $itemi; if ($linei1 eq $line1) { @matchone=split/ /, $linei[2]; $lengthandn=$l +ine[4].',', $line[5];` [download] ##error here--- Useless use of array element in void context--can u please tell me what this line does. `$matching{$matchone[0]}="$lengthandn"; $matching{$matchone[1]}="$lengthandn"; #$seenclone{$matchclone[1]}="1"; #print "678 line 1 $line[1] Length $l +engthandn matchclone $matchclone[1] m0 $matchclone[0]\n"; } }` [download] It seems to be missing portions though. All the variables and arrays should be declared at the beginning of the script (as far as I know). One other thing, all of the locations where a number was placed in square brackets were converted to links, and the square brackets disappeared. This is because you did not place your code between the `tags, so allways do that, please. <div class="pmsig"> <div class="pmsig-334202"> <br><br><code> our @item = reverse (114, 101, 107, 99, 97, 104, 32, 108, 114, 101, 80, 32, 114, 101, 104, 116, 111, 110, 97, 32, 116, 115, 117, + 74); local $my = reverse ")meti@\ ,rhc (pam tnirp";eval $my;` [download]	[reply] [d/l] [select]