Traversing succeding sets of an array

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

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Re: Traversing succeding sets of an array by thelenm (Vicar) on May 14, 2002 at 15:42 UTC
This may be one of those cases where an incremented index variable is useful: `for my $i (0..$#elements-1) { do_something_with($elements[$i],$elements[$i+1]); }` [download]	[reply] [d/l]
Re: Traversing succeding sets of an array by broquaint (Abbot) on May 14, 2002 at 15:34 UTC
You could take advantage of hashes `my %hash; push @{$hash{$_}}, $_ for @elements; foreach (keys %hash) { # gets passed an array reference, deref if you so desire do_something_with($hash{$_}) if scalar @{$hash{$_}} > 0; }` [download] Looks like you're dirtying your arguments there, maybe you want to have it return modified versions of the arguments e.g `my @data; foreach (keys %hash) { push @data, do_something_with($hash{$_}) if scalar @{$hash{$_}} > 0; }` [download] Or maybe you have a perfectly valid reason for doing what you're doing like logging the sets to a file. Better yet I could actually answer your question ... `my @elems = qw(foo bar baz quux ichi ni san shi go roku hachi); my $set = 3; while(scalar @elems) { do_something_with(splice(@elems, 0, $set)); }` [download] This however has the unfortunate side of effect of erasing the contents of the array, but does the job. HTH `_________ broquaint` update: the penny dropped ...	[reply] [d/l] [select]
Re: Traversing succeding sets of an array by bmcatt (Friar) on May 14, 2002 at 15:44 UTC
What about something like this? `do_something_with($elements[$_-1], $elements[$_]) foreach (1 .. $#elements);` [download]	[reply] [d/l]
Re: Traversing succeding sets of an array by strat (Canon) on May 14, 2002 at 15:40 UTC
Maybe splice is your friend: `my $elementsToGet = 2; # how many elements shell be in @sublist my @newElements = @elements; while (my @subList = splice(@newElements, 0, $elementsToGet)) { # do something with @subList } # while Beware that @newElements might be empty after the while...` [download] or, with a counter: `for (my $i=0; $i<=$#elements; $i+=2) { # do something with $elements[$i] and $elements[$i+1] } # for` [download] I haven't tested these codes. Best regards, perl -le "s==F=e=>y~\martinF~stronat~=>s~[^\w]~~g=>chop,print"	[reply] [d/l] [select]
Re: Re: Traversing succeding sets of an array by very empty (Scribe) on May 14, 2002 at 16:13 UTC
I do not have a even-sized list and I need to have to do also to do something with `($elements[$i=2*$j-1],$elements[$i+1])`	[reply] [d/l]
Re: Traversing succeding sets of an array by Util (Priest) on May 14, 2002 at 16:06 UTC
This works for $n between 1 and the number of elements, inclusive. It takes advantage of array slices when calling the subroutine. `sub do_something_with { print "@_\n"; } my @elements = qw( a b c d e f g ); my $n = 2; for my $i ($n-1 .. $#elements) { do_something_with(@elements[($i-($n-1))..$i]); }` [download] $n = 2 produces: `a b c b c d c d e d e f e f g` [download] $n = 4 produces: `a b c d b c d e c d e f d e f g` [download]	[reply] [d/l] [select]
Re: Traversing succeding sets of an array by boo_radley (Parson) on May 14, 2002 at 16:42 UTC
Yet another way, that works for exactly 2 elements. `my @foo = qw (one two three four five six seven eight nine ten); while ($c <$#foo){ ($s,$a)= @foo[$c++ .. ++$c+1]; print "$s $a\n"; }` [download]	[reply] [d/l]