Array looping advice

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

I need some help traversing my array of arrays. The output consists of position coordinates (x,y,z) and the selected values from the array. Also, the input array has to scale from 1D to nD ("3D" shown in the example). Thanks!

# input
my (@arr) = (
[ '0-0', '0-1' ],
[ '1-0', '1-1', '1-2', '1-3' ],
[ '2-0', '2-1', '2-2', '2-3' ]
);

# ...

# output
(0,0,0) --> 0-0 1-0 2-0
(0,0,1) --> 0-0 1-0 2-1
(0,0,2) --> 0-0 1-0 2-2
(0,0,3) --> 0-0 1-0 2-3
(0,1,0) --> 0-0 1-1 2-0
(0,1,1) --> 0-0 1-1 2-1
(0,1,2) --> 0-0 1-1 2-2
(0,1,3) --> 0-0 1-1 2-3
(0,2,0) --> 0-0 1-2 2-0
(0,2,1) --> 0-0 1-2 2-1
(0,2,2) --> 0-0 1-2 2-2
(0,2,3) --> 0-0 1-2 2-3
(0,3,0) --> 0-0 1-3 2-0
(0,3,1) --> 0-0 1-3 2-1
(0,3,2) --> 0-0 1-3 2-2 
(0,3,3) --> 0-0 1-3 2-3 
(1,0,0) --> 0-1 1-0 2-0
(1,0,1) --> 0-1 1-0 2-1
(1,0,2) --> 0-1 1-0 2-2
(1,0,3) --> 0-1 1-0 2-3
(1,1,0) --> 0-1 1-1 2-0
(1,1,1) --> 0-1 1-1 2-1
(1,1,2) --> 0-1 1-1 2-2
(1,1,3) --> 0-1 1-1 2-3
(1,2,0) --> 0-1 1-2 2-0
(1,2,1) --> 0-1 1-2 2-1
(1,2,2) --> 0-1 1-2 2-2
(1,2,3) --> 0-1 1-2 2-3
(1,3,0) --> 0-1 1-3 2-0
(1,3,1) --> 0-1 1-3 2-1
(1,3,2) --> 0-1 1-3 2-2 
(1,3,3) --> 0-1 1-3 2-3
[download]

Comment on Array looping advice Download Code

Replies are listed 'Best First'.
Re: Array looping advice by Corion (Patriarch) on Aug 11, 2008 at 08:15 UTC
See Algorithm::Permute and Algorithm::Loops, then show us your code and explain where you encounter problems. This is not a homework solution site.	[reply]
Re: Array looping advice by ikegami (Patriarch) on Aug 11, 2008 at 08:19 UTC
When you need loops nested arbitrarily deep, think of Algorithm::Loops's `NestedLoops`. If you just need the transformed values: `use Algorithm::Loops qw( NestedLoops ); my $i = NestedLoops(\@arr); while (my @vals = $i->()) { print(join(' ', @vals), "\n"); }` [download] If you need the indexes and transformed values: `use Algorithm::Loops qw( NestedLoops ); my $i = NestedLoops([ map { [ 0..$#$_ ] } @arr ]); while (my @idx = $i->()) { my @vals = map { $arr[$_][$idx[$_]] } 0..$#idx; print('(', join(',', @idx), ') --> ', join(' ', @vals), "\n"); }` [download]	[reply] [d/l] [select]
Re^2: Array looping advice by nineam (Initiate) on Aug 11, 2008 at 09:15 UTC
Thanks for you both! I hadn't run into Algorithm::Loops, but it seems to be very handy in cases like this. ...always, search CPAN first:)	[reply]