perl, help perl gurus!

phlx · 12-03-2004, 10:30 AM

Okay. I've Been tinkering with this code. My goal is to reverse the elements of an array, without using the reverse operator of course.

#!/usr/bin/perl

my @array = (1,2,3);

sub reverse_array {
my $arr_ref = shift;
my $rev_array = [];
foreach my $item (@$arr_ref) {
if (arr_ref($item) eq @array) {
$item = reverse_array($item);
}
unshift @$rev_array, $item;
}
return $rev_array;
}

reverse_array(@array);
print @array;

I am new to perl, so I pasted this together from various sources. A few things I dont understand if anyone could clarify, what does eq and arr_ref function as?
particularly, I don't understand this line of the code
if (arr_ref($item) eq @array)

Also, this code doesn't run successfully. Thanks in advance, Ryan.

sigsegv · 12-03-2004, 11:40 AM

Courtesy of google and perlmonks:

Code:

#!/usr/local/bin/perl -w
                                                                                
$i   = 0;
@arr = (1,2,3);
$mid = $#arr/2;
                                                                                
while ($i <= $mid) {
        $tmp        = $arr[$i];
        $rear       = $#arr-$i;
        $arr[$i]    = $arr[$rear];
        $arr[$rear] = $tmp;
        ++$i;
}
                                                                                
print @arr;

To answer your questions about the code you posted -- eq is like == (sort of). arr_ref isn't a function, it's a mistyped array name and index (should be $arr_ref[$item]). The line if (arr_ref($item) eq @array) is checking to see if $arr_ref[$item] is an array, and if it is, recuse into reverse_array with it.

phlx · 12-03-2004, 12:39 PM

sigsev, you are my hero

I have another perl question, but I don't want to flood the board with my perl cries so ill just pop it on here.

I'm trying to open a file with a standard format like
/x/y/z
then I want to read all the lines in the file and print an output of columns such that
X Y Z

So how could i scan a line and assign each category to an element in an array ?

sigsegv · 12-03-2004, 03:28 PM

Something like this?

Code:

while(<FILE>) {
        # Replace '/' with a tab
        s/\//\t/;
        # Print out the line
        print;
}

hk_linux · 12-03-2004, 11:06 PM

How abt split. If "/" is the delimiter, u can use the following sniipet

$a="1/2/3";
@b = split("/", $a);

The array b, will contain the values 1, 2 and 3.

HTH.

phlx · 12-04-2004, 06:04 PM

Well just in case you guys were wondering, here's what i ended up doing
the format of my file was
333-33-3333/First M. Last/2.5/Senior/2005

so i did this

#!/usr/local/bin/perl -w

use Tie::File;

tie @FILE, "Tie::File", 'file' or die $!;

unshift @FILE, "SSN\t\tFirst\tMiddle\tLast\tGPA\tStatus\tGrad. Yr.\n";

for(@FILE) {
s/ /\//g;
s/\//\t/g;

}
untie @FILE;