Assign valuse of array within array to variables

g_speran has asked for the wisdom of the Perl Monks concerning the following question:

Good Evening Perl Monks, How can one assign the contents of an array within a multi-dimensional array to a set of variables passed to a subroutine?

use warnings;
use Data::Dumper;

my @arr;
$arr[0][4] = (["S","M","R","B"]);

print Dumper @arr;

my ($VAR1,$VAR2,$VAR3,$VAR4) = @{$arr[0][4]}; 
print "Var1: $VAR1\tVar2: $VAR2\tVar3: $VAR3\tVar4: $VAR4\n";
Testing($arr[0][4]);

sub Testing () {
    my ($VAR5,$VAR6,$VAR7,$VAR8) = @{$_}; 
    print "Var5: $VAR5\tVar6:$VAR6\tVar7: $VAR7\tVar8: $VAR8\n";
}
[download]

OUTPUT
=================
main::Testing() called too early to check prototype at C:\temp\arr_ref
+ernce.pl line 11.
$VAR1 = [
          undef,
          undef,
          undef,
          undef,
          [
            'S',
            'M',
            'R',
            'B'
          ]
        ];
Var1: S Var2: M Var3: R Var4: B
Use of uninitialized value $_ in array dereference at C:\temp\arr_refe
+rnce.pl line 14.
Use of uninitialized value $VAR5 in concatenation (.) or string at C:\
+temp\arr_refernce.pl line 15.
Use of uninitialized value $VAR6 in concatenation (.) or string at C:\
+temp\arr_refernce.pl line 15.
Use of uninitialized value $VAR7 in concatenation (.) or string at C:\
+temp\arr_refernce.pl line 15.
Use of uninitialized value $VAR8 in concatenation (.) or string at C:\
+temp\arr_refernce.pl line 15.
Var5:   Var6:   Var7:   Var8:
[download]

Expecting output
==============
Var1: S    Var2: M    Var3: R    Var4: B
Var5: S    Var6: M    Var7: R    Var8: B
[download]

Comment on Assign valuse of array within array to variables Select or Download Code

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Re: Assign valuse of array within array to variables by LanX (Saint) on Feb 23, 2021 at 01:48 UTC
try `sub Testing { my ($VAR5,$VAR6,$VAR7,$VAR8) = @{$_[0]}; print "Var5: $VAR5\tVar6:$VAR6\tVar7: $VAR7\tVar8: $VAR8\n"; }` [download] `$_[0]` is the first element of the array `@_` `$_` is something completely different > main::Testing() called too early to check prototype at C:\temp\arr_refernce.pl line 11. Do `sub Testing {` not `sub Testing (){` if you want to pass arguments. Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery}	[reply] [d/l] [select]
Re^2: Assign valuse of array within array to variables by g_speran (Scribe) on Feb 23, 2021 at 03:23 UTC
Thank you kindly!	[reply]
Re: Assign valuse of array within array to variables by AnomalousMonk (Archbishop) on Feb 23, 2021 at 04:43 UTC
In general, it's a bad idea to use a prototype unless you know exactly what they do and why you're using it. See Far More than Everything You've Ever Wanted to Know about Prototypes in Perl -- by Tom Christiansen; also Prototypes in perlsub. Give a man a fish: `<%-{-{-{-<`	[reply] [d/l]
Re: Assign valuse of array within array to variables by BillKSmith (Monsignor) on Feb 23, 2021 at 21:15 UTC
The data structure that you create is probably not what you think. A lot goes on behind the scene in your initialization. I have expanded the initialization to more clearly show the same structure. The variable "@arr" is an array with only one element. That element is a reference to an anonymous array with five elements (The first four are undefined). The last element is a reference to an anonymous array with four elements (Your data). Dumper requires scalar arguments. You have provided an array. Perl expands this to a list with only one element (which is a reference). Dumper displays the object of that reference. The argument to Dumper should be a reference to @arr to force Dumper to parse the entire structure. I am not going to tell you how to get rid of the message about prototypes (You may be tempted to use them). Remove the prototype "()" from your subroutine definition. You are passing a single argument to the subroutine. That argument is a reference to an anonymous array. A subroutine finds its arguments in the array @_. You only have one argument so it is in $_[0]. You must dereference this to get your values. `use warnings; use Data::Dumper; my @array; @arr = ( [ undef, undef, undef, undef, ['S', 'M', 'R', 'B'], ] ); print Dumper \@arr; my ($VAR1,$VAR2,$VAR3,$VAR4) = @{$arr[0][4]}; print "Var1: $VAR1\tVar2: $VAR2\tVar3: $VAR3\tVar4: $VAR4\n"; Testing($arr[0][4]); sub Testing { my ($VAR5,$VAR6,$VAR7,$VAR8) = @{$_[0]}; print "Var5: $VAR5\tVar6: $VAR6\tVar7: $VAR7\tVar8: $VAR8\n"; }` [download] OUTPUT: `$VAR1 = [ [ undef, undef, undef, undef, [ 'S', 'M', 'R', 'B' ] ] ]; Var1: S Var2: M Var3: R Var4: B Var5: S Var6: M Var7: R Var8: B` [download] Bill	[reply] [d/l] [select]