subroutine - variable scope:

hello everyone:
I want to pass two numbers to a subroutine. within the subroutine add
two numbers and return the sum to calling function.

I have two files my_main.pl and my_sub.pl. the parameter's value
didn't pass to the subroutine. sum's value is always
zero.

I think i may not understood the value scope well in perl. Please
check my code and tell me how can I make this work.
Thanks for your help!

my_main.pl

#!/usr/bin/perl


use strict;
use warnings;

require "my_sub.pl";

my $x = 5;
my $y = 7;

my $result = addition($x, $y);
print $result;



my_sub.pl file

#!/usr/bin/perl
#a sub-routine used in my_main.pl

#Illegal character in prototype for main::addition $a, $b at
my_sub.pl line 11
#

use strict;
use warnings;

my $num1 = 0;
my $num2 = 0;

sub addition($num1,$num2)
{
my $answer = $num1 + $num2;
print "$answer is: $answer.n";
return $answer;

}

1;

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.

--- In perl-beginner%40yahoogroups.com">perl-beginneryahoogroups.com, "Jeff Shu" <santa98bn...> wrote:
&gt;
> sub addition($num1,$num2)
> {
> my $answer = $num1 + $num2;
&gt; print "$answer is: $answer.n&quot;;
&gt; return $answer;
> }

You have this part wrong. It must be like this:

sub addition {
my ($num1, $num2) = _;
return $num1 + $num2;
}

Optionally you can enforce that the subroutine gets two scalars by
giving the prototype:

sub addition($$) {
...
}

So in your case Perl complains about illegal chars in the prototype,
and you are adding up global $num1 and $num2, which are set to zero.

/sandy
http://myperlquiz.com/

Messages in this topic (2) Reply (via web post) | Start a new topic

.

--- In perl-beginner%40yahoogroups.com">perl-beginneryahoogroups.com, "Jeff Shu" <santa98bn...>
wrote:
>
&gt; hello everyone:
> I want to pass two numbers to a subroutine. within the subroutine
add
&gt; two numbers and return the sum to calling function.
>
> I have two files my_main.pl and my_sub.pl. the parameter's value
&gt; didn't pass to the subroutine. sum's value is always
> zero.
&gt;
> I think i may not understood the value scope well in perl. Please
&gt; check my code and tell me how can I make this work.
> Thanks for your help!
&gt;
> my_main.pl
>
> #!/usr/bin/perl
>;
>
> use strict;
> use warnings;
>
> require "my_sub.pl";
>
> my $x = 5;
> my $y = 7;
>
> my $result = addition($x, $y);
>; print $result;
>
>
>
> my_sub.pl file
>;
> #!/usr/bin/perl
>; #a sub-routine used in my_main.pl
>
> #Illegal character in prototype for main::addition $a, $b at
> my_sub.pl line 11
> #
>
> use strict;
> use warnings;
>
> my $num1 = 0;
> my $num2 = 0;
>
> sub addition($num1,$num2)
> {
> my $answer = $num1 + $num2;
&gt; print "$answer is: $answer.n&quot;;
&gt; return $answer;
>
> }
>
> 1;
>I'm a newbie at this but, if the sub returns '$answer'
shouldn't the main use '$answer' rather than '$result' ?

Messages in this topic (3) Reply (via web post) | Start a new topic

.

--- In perl-beginner%40yahoogroups.com">perl-beginneryahoogroups.com, "Jeff Shu" <santa98bn...>
wrote:
>
&gt; hello everyone:
> I want to pass two numbers to a subroutine. within the subroutine
add
&gt; two numbers and return the sum to calling function.
>
> I have two files my_main.pl and my_sub.pl. the parameter's value
&gt; didn't pass to the subroutine. sum's value is always
> zero.
&gt;
> I think i may not understood the value scope well in perl. Please
&gt; check my code and tell me how can I make this work.
> Thanks for your help!
&gt;
> my_main.pl
>
> #!/usr/bin/perl
>;
>
> use strict;
> use warnings;
>
> require "my_sub.pl";
>
> my $x = 5;
> my $y = 7;
>
> my $result = addition($x, $y);
>; print $result;
>
>
>
> my_sub.pl file
>;
> #!/usr/bin/perl
>; #a sub-routine used in my_main.pl
>
> #Illegal character in prototype for main::addition $a, $b at
> my_sub.pl line 11
> #
>
> use strict;
> use warnings;
>
> my $num1 = 0;
> my $num2 = 0;
>
> sub addition($num1,$num2)
> {
> my $answer = $num1 + $num2;
&gt; print "$answer is: $answer.n&quot;;
&gt; return $answer;
>
> }
>
> 1;
>I'm a newbie at this but, if the sub returns '$answer'
shouldn't the main use '$answer' rather than '$result' ?

Messages in this topic (4) Reply (via web post) | Start a new topic

.

No it should not. You see $answer is the inner value of the adder sub.
It's like this:

sub add {

my $result = $_[0] + $_[1];

return $result;

}

sub somethingelse {

my $thisresult = &add (1, 2);

print $thisresult;

}

These are two separate values. You are not in anyway forced to use the
same name or value that the other sub returns. Look a perl tutorial
about values, and returns

From: perl-beginner%40yahoogroups.com">perl-beginneryahoogroups.com
[mailto: perl-beginner%40yahoogroups.com">perl-beginneryahoogroups.com] On Behalf Of draktrax
Sent: Wednesday, March 19, 2008 6:10 AM
To: perl-beginner%40yahoogroups.com">perl-beginneryahoogroups.com
Subject: [PBML] Re: subroutine - variable scope:

--- In perl-beginner%40yahoogroups.com">perl-beginneryahoogroups.com
<mailto:perl-beginner%40yahoogroups.com> , "Jeff Shu" <santa98bn...>
wrote:
>
&gt; hello everyone:
> I want to pass two numbers to a subroutine. within the subroutine
add
&gt; two numbers and return the sum to calling function.
>
> I have two files my_main.pl and my_sub.pl. the parameter's value
&gt; didn't pass to the subroutine. sum's value is always
> zero.
&gt;
> I think i may not understood the value scope well in perl. Please
&gt; check my code and tell me how can I make this work.
> Thanks for your help!
&gt;
> my_main.pl
>
> #!/usr/bin/perl
>;
>
> use strict;
> use warnings;
>
> require "my_sub.pl";
>
> my $x = 5;
> my $y = 7;
>
> my $result = addition($x, $y);
>; print $result;
>
>
>
> my_sub.pl file
>;
> #!/usr/bin/perl
>; #a sub-routine used in my_main.pl
>
> #Illegal character in prototype for main::addition $a, $b at
> my_sub.pl line 11
> #
>
> use strict;
> use warnings;
>
> my $num1 = 0;
> my $num2 = 0;
>
> sub addition($num1,$num2)
> {
> my $answer = $num1 + $num2;
&gt; print "$answer is: $answer.n&quot;;
&gt; return $answer;
>
> }
>
> 1;
>I'm a newbie at this but, if the sub returns '$answer'
shouldn't the main use '$answer' rather than '$result' ?

[Non-text portions of this message have been removed]

Messages in this topic (5) Reply (via web post) | Start a new topic

.