global special variable for array index?

[Bobby Kleemann]

~sdpm~
On Thu, 20 Apr 2000, Bruce Timberlake wrote:

> ~sdpm~
> > Isn't there a global special variable for the list index when you're
> > stepping through a list with a for (= foreach) statement?  For
> > example, I frequently have code like this:
> > 
> > my $index;
> > for my $element (@list)
> > {
> >     # some processing on $element
> >     $index++;
> > }
> > 
> > It would be much easier if there were a global special variable (like
> > $. for line numbers) so I don't have to keep track of $index myself.
> 
> First off, with that syntax you want to be doing a "foreach," not "for."

You spell potatoe, I spell potato.  :-)  They both do the same thing in
this context.  Foreach is clearer, but for is quicker to type...

>  I don't think there is a special variable a la $_ for loop iteration
> counting. 

Unfortunately there isn't.  The reason is that when traversing a list with
the foreach loop, I think perl traverses it more like a linked list than
an actual array, so it never really knows what number in the chain it is,
only if it's at the begining, middle, or end.

> I think what would work for you is:
> 
>   $index = @list;
> 
> at the loop exit, which will set $index equal to the number of elements
> in @list.  E.g.,
>   my $index;
>   my $element;
>   @list = ("Larry", "Moe", "Curly");
>   foreach $element (@list) {
>     ... # process $element
>   }
>   $index = @list;  # $index now equals 3

This works only if you want the count at the end.  The way that was
originally proposed is the best way to do it, at least that I am aware
of.  

 _ _ _
 Bobby Kleemann <rkleeman at neta.com>
 http://www.neta.com/~rkleeman/

~sdpm~

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