Getting Value from joining 2 variables

[Noverast]

Please help me with the following. Here is my code:

    $pax_1="180";
    $pax_2="260";
    $pax_3="300"
    $pax_4="450";
    $maxadults = "3";
    
    $plus2 = "1";
        $currencycode = "ZAR";
    
    while ($maxadults >= $plus)
    {
    $paxing = "$pax_$plus";

    $sleeps = $sleeps . "$currencycode$paxing for $plus persons<br>";

    $plus++;
    }

I keep getting ZAR1 for 1 persons, ZAR2 for 2 persons, etc.. I've tried '' but then I get R$pax_$plus for 1 persons Pleas help.

[ELISHEVA]

Welcome to PerlMonks and Happy New Year!

It looks like you might be confusing variable names and strings. "$pax_$plus" simply creates a string. If $pax is "foo", and $plus is "100", then "$pax_$plus" creates the string "foo_100" "100" , not the variable $foo_100. (see moritz's reply below for why the resulting string is "100" and not "foo_100")

When you want to retrieve data associated with a series of consecutive numbers (i.e. 1 to 4), you need to use an array, like this:

# use these lines at the start to get Perl help you find
# bugs
use strict;
use warnings;

# Note: declare your variables with "my"
# This helps Perl catch any misspellings in variable names
# and reminds you to set initial values for everything

# price for 0, 1, 2, 3, 4 persons
my @pax = (0, 100, 260, 300, 450);
my $plus = 1;
my $currencycode = 'ZAR';
my $sleeps='';
my $maxadults = 4;

while ($maxadults >= $plus) {

  my $paxing = $pax[$plus];  #get $plus member of @pax array

  $sleeps = $sleeps . "$currencycode$paxing for $plus persons<br>";

  $plus++;
}

[moritz]

"$pax_$plus" simply creates a string. If $pax is "foo", and $plus is "100", then "$pax_$plus" creates the string "foo_100"

Not at all. It tries to look up the variable $pax_ (since an underscore is valid part of a variable name), and fails (and thus interpolates the empty string for $pax_).

use strict; use warnings; would have caught the problem, and can only be highly recommended to Noverast.

[ELISHEVA]

Good catch!

I frequently trip on that one and also $sClass::Blah when I mean ${sClass}::Blah. Thanks.

[mellon85]

or you could just be using

    my $name = "pax_$plus";
    $paxing = ${$name};

as it works without using strict refs like you do. But consider using strict and warning

[CountZero]

Very naughty. This is actually code which --undeservedly-- gives Perl a bad name.

[Noverast]

Thanks, This did the trick. I also included: use strict; use warnings;

[CountZero]

You set the variable $plus2 to one, but then you never use it and use $plus.

This type of error is one of the main reasons why you always should use strict; and use warnings; or useModern::Perl; (if you are using Perl 5.10 or later).

[fisher]

BTW, why don't you use the '.=' operator? This line

$sleeps = $sleeps . "$currencycode$paxing for $plus persons<br>";

transforms to

$sleeps .= "$currencycode$paxing for $plus persons<br>";

...and looks better, isn't it?