array sorting syntax question 1

[tonykent]

Can someone assist me with getting the correct syntax to sort this array please? I've tried all sorts and searched past threads but have not found the right answer.

I have a very complex and lengthy script that queries a database and eventually ends up with me having data in this format (this is 3 lines of data below - it doesn't display well so I have prefixed each line for clarity):

<line1> MOVE_top\general\major\captain\corp%1@MOVE_top%2.0_BL.01   corp%1:dir:pit01t     MOVE_top\general\major\captain
<line 2> MOVE_top\general\major%1@MOVE_top%2.0_BL.01                major%1:dir:pit01t    MOVE_top\general
<line3> MOVE_top\general\major\captain%1@MOVE_top%2.0_BL.01        captain%1:dir:pit01t  MOVE_top\general\major

I need to sort the lines based on the third field in each line.

#!/usr/contrib/bin/perl
use strict;
my @array;
my $x;
my $p=1;
while (<DATA>) {
  chomp;
  ($array[$p][1], $array[$p][2], $array[$p][3],) = split /\s+/;
  $p++;
}
close DATA;

for ($x=1;$x<$p;$x++) {
        #<do processing here: print to show line order>
	print "$array[$x][3]\n";
}

__DATA__
MOVE_top\general\major\captain\corp%1@MOVE_top%2.0_BL.01   corp%1:dir:pit01t     MOVE_top\general\major\captain
MOVE_top\general\major%1@MOVE_top%2.0_BL.01                major%1:dir:pit01t    MOVE_top\general
MOVE_top\general\major\captain%1@MOVE_top%2.0_BL.01        captain%1:dir:pit01t  MOVE_top\general\major

The code above simulates the data structure I have i.e $array[$p][1] $array[$p][2] $array[$p][3] for each line.

It currently gives the following output:

MOVE_top\general\major\captain
MOVE_top\general
MOVE_top\general\major

I need to sort each line based on $array[$p][3]so that it displays:

MOVE_top\general
MOVE_top\general\major
MOVE_top\general\major\captain

Can anyone help with the syntax to do this?

 

[ishnid]

print "$_\n" for sort map $array[$_][3], ( 1 .. $p - 1 );

 

[tonykent]

Wow, Ishnid, that was fast

That works a treat. Moving on from there, though, how would I write the old array into a new (sorted) array?

 

[ishnid]

It makes it easier if you start your arrays with index 0 (which is the usual way - is there some particular reason you're using 1?), rather than 1. You could do it like this:

@array = sort { $a->[3] cmp $b->[3] } @array;

If there's a reason for not using the first space in the array, you could do this to order everything from the second element on (i.e. from index 1 on). It's not very pretty, though

@array[1..$#array] = sort { $a->[3] cmp $b->[3] } @array[1..$#array];

 

[tonykent]

Thanks very much Ishnid. The last bit of code above was exactly what I needed - no wonder I didn't manage to come up with it myself.

 

[ishnid]

No problem.

I still think you should be beginning your array at 0 rather than 1, as that's the normal way arrays work. Even when you try to start using it at 1, there's still a position 0 which just doesn't have a value. The code becomes much cleaner (and a tiny bit more memory-efficient) that way. For example:

#!/usr/contrib/bin/perl
use strict;
my @array;
my $x;

while (<DATA>) {
  chomp;
  # split and add the result to the array
  push @array, [ split /\s+/ ];
}
close DATA;

# sort the array
@array = sort { $a->[2] cmp $b->[2] } @array;

for ( @array ) {
   print "$_\n";
}