> ²) a c-style for is semantically just a while-loop with a prior declaration.

to expand further on this, please see perlsyn#For-Loops

which means 

        for (my $i = 1; $i < 10; $i++) {
            ...
        }

[download]
is the same as this:

    {
        my $i = 1;
        while ($i < 10) {
            ...
        } continue {
            $i++;
        }    
    }

[download]

now compare the different effects from an inner declaration ($i) and an outer declaration ($x) 

use strict;
use warnings;


# ---------- for c-style

my @cfor;

for ( my $x = 1 ; $x < 4; $x++ ) {
    my $i = $x;
    push @cfor, sub { warn "cfor: \ti=$i \tx=$x" };
}

$_->() for @cfor;


# ---------- while

my @values = 1..3;
my @while;

my $x;
while ( my $i = shift @values ) {
    $x = $i;
    push @while, sub { warn "while: \ti=$i \tx=$x" };
}

$_->() for @while;

[download]
cfor:     i=1     x=4 at d:/exp/pm_closure2.pl line 11.
cfor:     i=2     x=4 at d:/exp/pm_closure2.pl line 11.
cfor:     i=3     x=4 at d:/exp/pm_closure2.pl line 11.
while:     i=1     x=3 at d:/exp/pm_closure2.pl line 25.
while:     i=2     x=3 at d:/exp/pm_closure2.pl line 25.
while:     i=3     x=3 at d:/exp/pm_closure2.pl line 25.

[download]

Cheers Rolf
(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery FootballPerl is like chess, only without the dice

In reply to Re^2: Closure confusion in Tkx (declarations in loops - inner vs outer) by LanX
in thread Closure confusion in Tkx by lbrandewie

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