Re: Difference between for and foreach


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Re: Difference between for and foreach

by Hercynium (Hermit)

on Sep 17, 2007 at 15:42 UTC ( [id://639435]=note: print w/replies, xml )

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in reply to Difference between for and foreach

I'm pretty certain that Joost is correct at least as far as the specifications of how each construct is supposed to work.

I'd like to add that it's worth paying attention to the aliasing behavior in certain situations, where the loop iterator variable ($thing in this example)
for my $thing (@things) { # do stuff to $thing # }
is not a copy of the current element of @things but more like a reference (a magic one that does not need to be de-referenced). The side effects have bitten me in the past, before I learned better :)

Also, I've just been reading Perl Best Practices by TheDamian and chapter 6 (around pg. 100) goes in-depth on some of the techincal *and* psychological implications of different ways of using for and it's brethren.

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Re^2: Difference between for and foreach
by johngg (Canon) on Sep 18, 2007 at 09:00 UTC

foreach

last

$ perl -Mstrict -Mwarnings -le '
> my $x = 0;
> print $x;
> for $x ( 1 .. 10 )
> {
>     my $y = rand;
>     print qq{$x -- $y};
>     last if $y > 0.85;
> }
> print $x;'
0
1 -- 0.820319728766666
2 -- 0.070987764836417
3 -- 0.632845876776752
4 -- 0.195428179899814
5 -- 0.847997411282524
6 -- 0.353572570937089
7 -- 0.865375393672675
0
$
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You have to preserve the loop variable from inside the loop if you need to access it afterwards.

Cheers,

JohnGG

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