[newbie] scope of the variables

[John]

Hi all,


I am trying to create a module. and I have a question about the scope
of the variables.



lets say,

use strict;


sub one {

my ($rvalue) = @_; # here I define a variable

for my $i (0..$#$rvalue){ # here I define a local
# variable $i and I use it

# do something
}

}


sub second {

my ($rvalue) = @_; # on this second sub $rvalue
# is a new one or I carry it
# as the first one


for my $i (0..$#$rvalue){ # now the same case, $i was
# already defined and if the
# scope is just its
# own subsroutine, now this
# $i is something copletely
# new. Am I right?

# do something else
}
}


# Thanks for your help
# John

 

[Tad McClellan]

I am trying to create a module. and I have a question about the scope
of the variables.

None of the variables in your module code below will be visible
in the "use"ing program, they are all "lexical variables".

Learn all about Perl's two separate systems of variables at:

"Coping with Scoping":

http://perl.plover.com/FAQs/Namespaces.html

for my $i (0..$#$rvalue){ # here I define a local ^^^^^
# variable $i and I use it

^^^^^^^^

(I can't say "for" for "foreach". I reserve "for" for for(;


In Perl, local() has to do with _package_ variables, which are
a form of _global_ variable, so it is confusing to use "local"
to mean "local". or should it be :-( ?

You have defined a _lexical_ variable.

Lexical variables (my) always get you a completely new variable,
new memory allocated and all.

So, yes, $i will be visible only within the body of the foreach() block.

When the (foreach) block exits, $i will cease to exist.

for my $i (0..$#$rvalue){ # now the same case, $i was
# already defined and if the
# scope is just its
# own subsroutine, now this
# $i is something copletely
# new. Am I right?

You are right.