tcl like 1 loop with two operators

ISAI student has asked for the wisdom of the Perl Monks concerning the following question:

Hello all. I have been using Tcl as an EE, and using PERL. Tcl has a way of looping with two iteration variables: It looks something like this:

foreach i {1 2} j {3 4} {
  puts $i
  puts $j

}
[download]

The machine would output:

1
3
2
4
[download]

W/o a need for an integer iterator. The language engine checks for list/array length. Is there something similar in PERL?

Comment on tcl like 1 loop with two operators Select or Download Code

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Re: tcl like 1 loop with two operators by Corion (Patriarch) on Jan 24, 2011 at 12:58 UTC
I'd use List::MoreUtils::natatime ("n at a time"): `my $it = natatime 3, 1,2,3,4; while (my $i, $j = $it->()) { ... };` [download] ... or, if you have the data in two lists already, List::MoreUtils::pairwise (or ::each_arrayref, but have a look List::MoreUtils yourself) `pairwise { print $a; print $b; } @a, @b` [download]	[reply] [d/l] [select]
Re^2: tcl like 1 loop with two operators by AnomalousMonk (Archbishop) on Jan 24, 2011 at 17:30 UTC
E.g., with List::MoreUtils`::each_array()`: `>perl -wMstrict -le "use List::MoreUtils qw(each_array); my @ra = qw(a b c); my $pair_iter = each_array @ra, @{[ qw(x y z) ]}; while (my ($i, $j) = $pair_iter->()) { print qq{$i, $j}; } " a, x b, y c, z` [download]	[reply] [d/l] [select]
Re: tcl like 1 loop with two operators by JavaFan (Canon) on Jan 24, 2011 at 13:26 UTC
Not natively. I would write that as: `foreach my $fred ([1, 3], [2, 4]) { my($i, $j) = @$fred; say $i; say $j; }` [download]	[reply] [d/l]
Re^2: tcl like 1 loop with two operators by Mask (Pilgrim) on Jan 25, 2011 at 15:14 UTC
Or in case if arrays with $i and $j values are predefined, I would write it like that: `my @i=(1,2); my @j=(3,4); my @a = map {[$i[$_],$j[$_]]} 0..$#i; foreach my $ij (@a){ my ($i, $j) = @{$ij}; say $i; say $j; }` [download] OR if it's necessary to emulate TCL behaviour for different lengths of arrays with $i and $j values, I would write it like that: `my @i=(1,2); my @j=(3,4,5); my @len = sort(scalar(@i),scalar(@j)); my @a = map {[$i[$_],$j[$_]]} 0..$len[-1]; foreach my $ij (@a){ my ($i, $j) = @{$ij}; print $i."\n"; print $j."\n"; }` [download]	[reply] [d/l] [select]
Re: tcl like 1 loop with two operators by Fletch (Bishop) on Jan 24, 2011 at 13:31 UTC
Algorithm::Loops might also be of interest. The cake is a lie. The cake is a lie. The cake is a lie.	[reply]