On Tue, Jul 05, 2005 at 08:05:11AM +0200, Jean-Luc VERIT wrote:
> But
> you told me "Dont used $_ in nested loops", But I wrote thousands lines of
> Perl, and I used and abused using $_ in nested loops, and the
> only time it didn't work is when it is used with this sequence.
> first "$_" related to name of file from an array with a foreach,
> second open this file,
> third read this file with the second $_ and "while(<FIL>){ ....."
>
> It is said some where in the Camel book (in the second and in the third
> edition) that each loop has its own instance of "$_", and it always works
> like this, but in the case I mentionned.
Only for loops auto-localize $_. A while loop has no intrinsic $_ assignment.
Its a bit of magic associated with the <FH> operator. This is the reason
you only seem to run into the problem while reading files, its rare to use
$_ in a while loop otherwise.
It may be worthwhile investigating if auto-localizing $_ in a while(<FH>)
construct is worth adding to the language.
Anyhow, stick to "foreach my $thing (@things)" for anything but the smallest
loops and you'll be ok.
> An other point (may be related to this) : I wrote about 2 or 3 hundred of
> thousands lines of Perl, but I'm still confused with FILES in PERL. It seems
> to me to be like a patch added to the language. It could be an explanation
> of the problem, as the first instance of "$_"is created by a "foreach"
> (which seems to me very robust), ans the second instance is created by the
> "while(<FIL>){ ....."
Let's just say file handling is showing its age and hacks.
--
Michael G Schwern [EMAIL PROTECTED] http://www.pobox.com/~schwern
Just call me 'Moron Sugar'.
http://www.somethingpositive.net/sp05182002.shtml
