Update: You have a terrible error that's one of my hobbyhorses, and I missed it on the first cut :( $a is sacred to sort

You're assigning a whole new %list each time around.

while(<TEST>){
    chomp;
    /(\w+)\s+(\w+)/;
    print "$i : $2\,$1\n";
    $list{$i} = [$1,$2];
    $i+=1;
}
[download]

foreach my $c (sort keys %list) {
    print "$list{$c}->[1],$list{$c}->[0]$/"
}
[download]

Update: Softened statement on dereferencing and corrected horrible error mixing $a as temporary with sort.

Update 2: Here's a line to sort and print all at once

print map {"$_->[1], $_->[0]$/"} sort {lc($a->[1]) cmp lc($b->[1])} va
+lues %list;
[download]

After Compline,
Zaxo

Thank's, that worked well, except it doesn't display the last names alphabetically... I'm not quite sure what the problem is--I think it may have to do something with the keys being numbers, and we are telling it to sort by them. This is my first time using associatve arrays, so bare with me :P...anyway here's the new code:

#!/usr/bin/perl -w 

use strict;

open(TEST, 'test.txt') || die "Couldn't open it";
print "\nFile Opened\n\n\n";
my $i=1;
my %list;
while(<TEST>){
    chomp;
    /(\w+)\s+(\w+)/;
    print "$i : $2\,$1\n";
    $list{$i} = [$1,$2];
    $i+=1;
}

foreach my $c (sort keys %list) {
    print "$list{$c}->[1],$list{$c}->[0]$/"}



close(TEST);
die "\n\n\nFile Closed\n";
[download]

Input file:


Emmitt Smith
Walter Payton
Barry Sanders
Jim Brown
Jeremy Smith

Oh yeah, what do you mean by dereferencing?

Thanks,
Emmitt

Your second take is much better, much more indented, but try and keep things neat. Your closing brace in your foreach, for example, is strangely at the end of a line which is also sans-semicolon.

Anyway, to "derefence" something is to take a reference and use it to obtain a value. References are what make people exposed to C for the first time look all green and dizzy, but they're really not that bad, especially in Perl.

Here's a really, really brief introduction to references:

my @array      = qw[ 1 2 3 ];
my $array_ref  = \@array;      # Backslash makes a reference
my @array_copy = @$array_ref;  # @ de-references array reference

$array[2]       = 4;   # Modifies @array directly
print $array_ref->[2]; # Should be '4' now
$array_ref->[1] = 5;   # Modifies @array by reference
print $array[1];       # Should be '5'
$array_copy[1]  = 6;   # Modifies @array_copy, not @array
print $array[1];       # Still '5'
[download]

For a much more detailed document, check out perlref.

Fortunately, or unfortunately depending on your opinion, Perl will automagically dereference for you in certain circumstances. Where $foo->{bar} is actually an "ARRAY" reference, you should really sub-address that as $foo->{bar}->[1] and not $foo->{bar}[1], but either should work.

#!/usr/bin/perl -w
use strict;

my $i = 1;
my %list;

open TEST, 'test.txt' || die "Couldn't open it";
print "\nFile Opened\n\n\n";
while(<TEST>){
    chomp;
    my ($f, $l) = split(' ', $_, 2);     
    print "$i : $l\,$f\n";
    $list{$i} = [$f,$l];
    $i += 1;
}

foreach my $c (sort keys %list) {
    print "$list{$c}->[1],$list{$c}->[0]$/";
}

close TEST;
print "\n\n\nFile Closed\n";
[download]

Also, may I ask why $list{$c}->[1],$list{$c}->[0] and $list{$c}[1],$list{$c}[0] are not really the same thing?
Is it because without the dereferencing arrows, it is not "technically correct" code?
I have never used the arrows and my code has always worked fine!

$ cat test.txt | sed -e's/\(.*\) \(.*\)/\2,\1/g' | sort
Brown,Jim
Payton,Walter
Sanders,Barry
Smith,Emmitt
[download]

cat test.txt | sed -e's/\(.*\) \(.*\)/\2,\1/g' | sort
[download]

And that would be not only a Useless Use of Cat, but not taking advantage of sort's field sorting abilities either:

$ sort +1 -2 +0 -1 <test.txt >output.txt
[download]

-- Randal L. Schwartz, Perl hacker

Hmmm ... maybe we can have a golf game?
What would be shorter a shell script or a perl script?
My money would be on the shell script. What do you think merlyn?