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Re: Lexical closures

by chromis (Novice)
on Oct 27, 2008 at 20:09 UTC ( #719824=note: print w/replies, xml ) Need Help??


in reply to Lexical closures

Hello,

This is my first post ;)

Perhaps this snippet of code is also convenient for a better understanding. I always like to print references in order to understand such things:

#!/usr/bin/perl use strict; use warnings; use feature qw/say/; my @array = (1, 2, 4, 8, 16, 32, 64, 128); foreach my $elem (@array) { say \$elem; # this *doesn't* print a unique number for all iterati +ons! $elem *= 2; } say join(', ', @array); say join(', ', map(\$_, @array)); # ..surprisingly familiar! @array = qw/x y z/; say join(', ', @array); say join(', ', map(\$_, @array)); # ..surprisingly familiar too! say \@array[0];
The output at my machine is:
SCALAR(0x8153220) SCALAR(0x8153360) SCALAR(0x8153100) SCALAR(0x817bcb8) SCALAR(0x817bcc8) SCALAR(0x818ea18) SCALAR(0x81886d0) SCALAR(0x8188fd0) 2, 4, 8, 16, 32, 64, 128, 256 SCALAR(0x8153220), SCALAR(0x8153360), SCALAR(0x8153100), SCALAR(0x817b +cb8), SCALAR(0x817bcc8), SCALAR(0x818ea18), SCALAR(0x81886d0), SCALAR +(0x8188fd0) x, y, z SCALAR(0x8153220), SCALAR(0x8153360), SCALAR(0x8153100) SCALAR(0x8153220)
edit: this may also be of interest
my $i = 123; say $i . ' ' . \$i; foreach $i (1 .. 3) { say $i . ' ' . \$i; } say $i . ' ' . \$i;
output:
123 SCALAR(0x817bd18) 1 SCALAR(0x8153220) 2 SCALAR(0x8153220) 3 SCALAR(0x8153220) 123 SCALAR(0x817bd18)
The reason why the scalars are the same inside the foreach in this particular occasion is because I'm now iterating over a list and not an array. I've always assumed that there is a difference, and that lists only exist in Perl source code and that they are solely used for initialization of other things such as arrays (and hashes). Is this correct?

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