PERL: comparing if a set of variables have the same value

This post originates because I was reading a post from PerlMongers back in 2001

I posted here because the perlish way of using double negation logic in '!grep != ' or the trick to encode the variables to a string and check what it remains after removing a string. Sometimes this tricks would be useful (despite not pretty).

In response to draegtun comment:

Thanks for the Perl6::Junction hint. But probably I will go for List::MoreUtils

DB<8> use List::MoreUtils qw(any all)

DB<2> $a=1; $b=1;$c=1;$d=1;$e=1;$z=2

DB<9> (all{$_ ==$a} ($a,$b,$c,$d,$e, $z))? print "doing st because equal\n" : print "sorry not equal\n"
sorry not equal

DB<10> (all{$_ ==$a} ($a,$b,$c,$d,$e))? print "doing st because equal\n" : print "sorry not equal\n"
doing st because equal

 in reply to Re:
Re: Re: Fastest way to compare multiple variables?
in thread Fastest
way to compare multiple variables?
on May 15, 2001 at 21:10 UTC ( #80620=perlquestion: print w/ replies,
xml )
Anonymous Monk
has asked for the wisdom of the Perl Monks concerning the following
question:

Hi, Is there anyway (without using hashes) to do
something like
if ($a == $b == $c == $d) {
&do_something
}
What I have: 15-20 variables ALREADY have their values (integers)
What I need: tell if all those variables have a same value or not
What I know: there are already ways to do that by using arrays/hashes.
Or, hash is still the fastest way? Thank you...
TIMTIWODI 1:
Re:
Fastest way to compare multiple variables?
by Masem (Monsignor) on May 15, 2001 at
21:14 UTC

TIMTOWODI:
if ( !grep { $_ != $a } ($b, $c, $d, $e...) ) { &do_something }
[download]

---

Dr. Michael K. Neylon - mneylon-pm@masemware.com || "You've left the lens cap of your mind on again, Pinky" - The Brain

TIMTIWODI 2: Merlin way:

on May 15, 2001 at 21:51 UTC ( #80645=note: print w/ replies,
xml )

use CGI;
@array1 = param('datalist1');
@array2 = param('datalist2');
@array3 = param('datalist3');

[download]

If you could make that instead:

my %data = map { $_ => [param $_] }
qw(datalist1 datalist2 datalist3);

[download]

Then we can compare their lengths
with:

sub compare {
my @lengths = map { scalar @{$data{$_}} } qw(datalist1 datalist2 dat
+alist3);
my $first = shift @lengths;
$first == $_ or return 0 for @lengths;
return 1;
}

[download]

See how much easier? Regularity in
variable names is almost always a sign that they should be part
of a larger structure instead. -- Randal L. Schwartz, Perl
hacker

TIMTIWODI 3: using s///g . Probably it is slower if you have a
lot of values but the idea of eliminating things and count how many
remain doing it in a string instead with a grep is 'another way of
doing it'

Re: Re: Fastest way to compare multiple variables? by zeidrik (Scribe) on May 16, 2001 at 11:58 UTC

Try this:

#!/usr/local/bin/perl -w
use strict;
my @list=("abcd123","abcd143","abcd123","abcd123");
$_=join("",@list);
s/$list[0]//g;
print "not equal\n" if ($_);