Re^5: Using an array element as a loop iterator

Oh, it's far clearer with the nested loops example ^^. You could also do:

for(@a1=`cat file`;$a[0]=shift @a1;@a1)
{
  for(@a2=@b;$a[1]=shift @a2;@a2) # could be "for(;$a[1]=shift @b;@b)"
+ if you don't care about emptying @b
  {
    for(@a3=grep /4/, @c;$a[2]=shift @a3;@a3)
    {
      <Statements>;
    }
  }
}
[download]

but that's kind of ugly. Maybe you could use that with source filtering to have a lighter syntax ...

If you intend to do that sort of things often in your script you could use Perl Prototypes to add that kind of syntax to your program:

sub with {for (@{$_[1]}){$_[0] = $_;$_[2]();}}
sub in { \@_  } 
sub run(&) { $_[0] }
[download]

Then you could write :

# parenthesis mandatory after in, bad idea after with and the commas c
+an't be ommited
with $a[0], in(qw/Bonjour Bonsoir/), 
run {
    with $a[1], in ("Paul", "Jack", "Lord Voldemort"),
    run {
        say "@a";
    }; # semi-colon mandatory
}; # same here
[download]

Bonjour Paul
Bonjour Jack
Bonjour Lord Voldemort
Bonsoir Paul
Bonsoir Jack
Bonsoir Lord Voldemort
[download]

But I did that because it was fun, and a bit of a challenge, but that's not very practical. You probably have to stick with my first answer.

Comment on Re^5: Using an array element as a loop iterator Select or Download Code

Replies are listed 'Best First'.
Re^6: Using an array element as a loop iterator by LanX (Saint) on Nov 08, 2013 at 19:45 UTC
> but that's kind of ugly. maybe easier written with while loops? `while ($a[0] =shift @a1) { ... }` ... well at least for me better readable :) Cheers Rolf ( addicted to the Perl Programming Language)	[reply] [d/l]
Re^7: Using an array element as a loop iterator by Eily (Monsignor) on Nov 08, 2013 at 20:14 UTC
It surely is ^^. The problem is that you can't use that construct like this: while( $a[0] = shift `cat file` ) (but that is a unusual way to read a file, indeed). So you do have to set @a1 first, which is the first part of my for loop. And if @a1 contains a value that is false, `$a[0] = shift @a1` will be false as well, so the loop will stop early. `defined($a[0] = shit @a1)` would work, unless you want to use undef as a value. That's why I used @a1 in scalar context as the third part of the for loop.	[reply] [d/l] [select]
Re^8: Using an array element as a loop iterator by LanX (Saint) on Nov 08, 2013 at 20:19 UTC
agreed! ++ =) Cheers Rolf ( addicted to the Perl Programming Language)	[reply]
Re^7: Using an array element as a loop iterator by gurpreetsingh13 (Scribe) on Nov 09, 2013 at 08:59 UTC
Thanks a lot. Got the point.	[reply]


"be consistent"
	PerlMonks