Working with Arrays

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

Hi all, Little lost with this problem. I have an input file similar to

18   56
25   10
12   45
[download]

First Column is called PDB second PIC. If i have a sumber stored in $NUM17 = 25. I need to make sure that $NUM17 appears in column one then print its corresponding PIC, column 2 number. I thought something along:

while (<DATA>) {
($PDB, $PIC) = split (/\s+/, $_) if (/^\d+.*/);
               }
@pic = $PIC;
@pdb = $PDB;
$endpdb = scalar @pdb;

for ($count = 0; $count < $endpdb; count++;) {

if ($PDB == $NUM17)  {$value = $pic[$count]};

}
[download]

thanks, #print "$value\n";

Comment on Working with Arrays Select or Download Code

Replies are listed 'Best First'.
Re: Working with Arrays by davorg (Chancellor) on Jul 07, 2004 at 12:25 UTC
Why make it so complex :) `while (<DATA>) { print +(split)[1], "\n" if /^$NUM17\b/; }` [download] -- <http://www.dave.org.uk> "The first rule of Perl club is you do not talk about Perl club." -- Chip Salzenberg	[reply] [d/l]
Re^2: Working with Arrays by Anonymous Monk on Jul 07, 2004 at 12:30 UTC
thanks Dave this will do the job!	[reply]
Re: Working with Arrays by naChoZ (Curate) on Jul 07, 2004 at 12:06 UTC
This smacks of homework, but... I think in this case you probably want a hash, not an array, assuming PIC will not have duplicates. `my %foo = ( 18 => 56, 25 => 10, 12 => 45, .. ); print $foo{ 18 };` [download] -- Diplomacy is the art of saying "Nice doggie" until you can find a rock. naChoZ	[reply] [d/l]
Re^2: Working with Arrays by Anonymous Monk on Jul 07, 2004 at 12:10 UTC
not homework just trying to learn and apply perl, beyond the stage of homework problem is that this is not suitbable, as the file could be 1000 lines long	[reply]
Re^3: Working with Arrays by revdiablo (Prior) on Jul 07, 2004 at 17:46 UTC
this is not suitbable, as the file could be 1000 lines long 1000 lines is not all that long. This should be plenty small enough to load into memory, as long as you're not on a very limited system. As a test, you can try loading up hashes with different numbers of elements, and looking to see what the memory usage is: `perl -e 'my %hash = map {$_=>$_} 1 .. 1_000; print "done"; sleep' perl -e 'my %hash = map {$_=>$_} 1 .. 10_000; print "done"; sleep' perl -e 'my %hash = map {$_=>$_} 1 .. 100_000; print "done"; sleep'` [download] On my system, the version that loaded 100,000 numbers used 21mb of memory. The version that loaded 1,000 numbers only used 3mb. On any modern computer, this should be a reasonable amount.	[reply] [d/l]
Re: Working with Arrays by naChoZ (Curate) on Jul 07, 2004 at 12:17 UTC
Populate the hash in your while loop. `my %foo; while (<DATA>) { .. $foo{ $PIC } = $PDB; }` [download] -- Diplomacy is the art of saying "Nice doggie" until you can find a rock. naChoZ	[reply] [d/l]