Not Coder reference error - when i pass function by Refernce

pks283 has asked for the wisdom of the Perl Monks concerning the following question:

Hi, i need help with below implementation of passing function by reference. I am passing add function to multiply function. It executes first time correctly, but fails next time executing function passed by reference. I have played with code and not able to figure out what i am missing. Below is my code.

use strict;
use warnings;


our $static_counter = 1;

sub add{
    
    my ($x, $y) = @_;
    my $sum = $x + $y;
    print "Sum within function: $sum\n";    
    return ($sum);
}

sub counter {
    my $cnt = $static_counter++;
    print "Value of count in subroutine  $cnt\n";
    return($cnt);
}

sub multiply{
    my ($x, $y, $add_ref, $counter_ref) = @_;
    
    my $cnt_in;
    my $add_in;
    my $mul = 1;
    

    
    $mul = ($x * $y * $$add_ref * $counter_ref->());
    print "Multi : $mul\n";    
    
    $add_in = $add_ref->(20,5);  ### Getting Error Here 
    ###  Not a Code Reference
    $mul = ($x * $y * $add_in * $counter_ref->()); 
    print "Multi : $mul\n";         
    
    return $mul;
    
}

sub a {    
    my $z; 
    
    $z =  multiply(4,5, \&add(10,1), \&counter);
    $z =  multiply(4,5, \&add(10,1), \&counter);
}

a();
[download]

Comment on Not Coder reference error - when i pass function by Refernce Download Code

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Re: Not Coder reference error - when i pass function by Refernce by huck (Prior) on Feb 25, 2017 at 22:34 UTC
`use strict; use warnings; sub add{ my ($x, $y) = @_; my $sum = $x + $y; print "Sum within function: $sum\n"; return ($sum); } my $bb=\&add(10,1); print $bb."\n"; my $cc=\&add; print $cc."\n";` [download] Result `Sum within function: 11 SCALAR(0x3f7e24) CODE(0xa3e58c)` [download] `\&add(10,1)` is not a code reference but a reference to the result of `&add(10,1)` use strict; use warnings; our $static_counter = 1; sub add{ my ($x, $y) = @_; my $sum = $x + $y; print "Sum within function: $sum\n"; return ($sum); } sub counter { my $cnt = $static_counter++; print "Value of count in subroutine $cnt\n"; return($cnt); } sub mm{ my ($x, $y, $add_ref, $counter_ref) = @_; my $cnt_in; my $add_in; my $mul = 1; $mul = ($x * $y * &$add_ref(10,1) * &$counter_ref()); print "Multi : $mul\n"; $add_in = $add_ref->(20,5); ### Getting Error Here ### Not a Code Reference $mul = ($x * $y * $add_in * $counter_ref->()); print "Multi : $mul\n"; return $mul; } sub aa { my $z; $z = mm(4,5, \&add, \&counter); $z = mm(4,5, \&add, \&counter); } aa(); [download] result `Sum within function: 11 Value of count in subroutine 1 Multi : 220 Sum within function: 25 Value of count in subroutine 2 Multi : 1000 Sum within function: 11 Value of count in subroutine 3 Multi : 660 Sum within function: 25 Value of count in subroutine 4 Multi : 2000` [download]	[reply] [d/l] [select]
Re^2: Not Coder reference error - when i pass function by Refernce by pks283 (Novice) on Feb 25, 2017 at 23:16 UTC
Thanks for feedback	[reply]
Re^3: Not Coder reference error - when i pass function by Refernce by Marshall (Canon) on Feb 26, 2017 at 21:09 UTC
FYI, There is an alternate syntax using the arrow operator when calling a reference to a sub, e.g.: `#$mul = ($x * $y * &$add_ref(10,1) * &$counter_ref()); $mul = ($x * $y * $add_ref->(10,1) * $counter_ref->());` [download]	[reply] [d/l]
Re^4: Not Coder reference error - when i pass function by Refernce by stevieb (Canon) on Feb 26, 2017 at 21:36 UTC
Re: Not Coder reference error - when i pass function by Refernce by Anonymous Monk on Feb 25, 2017 at 23:11 UTC
`\&add(10,1)` is not a reference to `sub add` with the parameters, it's `\( &add(10,1) )`, so a reference to the return value of `&add(10,1)`, so `\11`. If you want to do something like Currying, write `sub { add(10,1) }` instead.	[reply] [d/l] [select]