'defined' function

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

Hi Monks, I am pushing certain elements of one array into another array but the program is struggling if/when these elements don't exist. I thought about using the defined function for this but wondered if there was a quick way to check for each element and then if it is defined, push it into the array. Thanks ;->


if ($p ==1)   {

  push @points, "$peaks[7] $peaks[8] $peaks[9] $peaks[10] $peaks[11] $
+peaks[12] $peaks[13]";

}
[download]

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Re: 'defined' function by broquaint (Abbot) on Jun 13, 2003 at 10:43 UTC
It depends on how you want to deal with the empty elements, but a `grep` should do the job there e.g `push @points, join ' ', grep defined, @peaks[7 .. 13];` [download] See. the `grep docs` for more info. HTH `_________ broquaint`	[reply] [d/l]
Re: 'defined' function by Zaxo (Archbishop) on Jun 13, 2003 at 10:51 UTC
This assumes that the elements you want to push are at the end of the array, and that undefined ones come from the array being short. `if ($p == 1 ) { push @points, @peaks[7..$#peaks]; }` [download] That makes use of an array slice to avoid the repetitive list of elements. The $#peaks variable is a builtin carrying the last index of the array. (Update) The grep solutions are more general since they also work for arrays with holes in them. The last index trick is useful with them, too. After Compline, Zaxo	[reply] [d/l]
Re: 'defined' function by ChOas (Curate) on Jun 13, 2003 at 10:48 UTC
Something like this ? : `push @points,grep {defined} @peaks[7,8,9,10,11,12,13];` [download] OR (as you seem to have written:) `push @points,join " ",grep {defined} @peaks[7,8,9,10,11,12,13]` [download] -edit- too late :) GreetZ!, ChOas print "profeth still\n" if /bird\|devil/;	[reply] [d/l] [select]
Re: 'defined' function by EvdB (Deacon) on Jun 13, 2003 at 10:51 UTC
This should do it: `# Test me - i do not have the data. my $string; for (7..13) { next unless defined $peaks[$_]; $string = join ' ', $string, $peak[$_]; } push @points, $string;` [download] --`tidiness is the memory loss of environmental mnemonics`	[reply] [d/l] [select]