[Chicago-talk] map and pop

[Steven Lembark]

-- "Dooley, Michael" <Dooley.Michael at con-way.com>

> I want to do something like this, but I also want to remove the found
> element from @files.
>
> my @nfiles=grep /^car/, @files;
>
> can anyone point me in the right direction, I am thinking map is needed
> but I don't have much confidence using it.

	my @nfiles = ();

	@files = map { /$regex/ ? do {push @nfiles, $_; ()} : $_ } @files;

e.g.,

  DB<7> @a = (1..10)

  DB<8> @b = ()

  DB<10> x @a = map { $_ % 2 ? do{push @b, $_; ()} : $_ } @a
0  2
1  4
2  6
3  8
4  10
  DB<11> x @b
0  1
1  3
2  5
3  7
4  9


Other way would be a hash, which might be a bit easier for
anyone who follows you to figure out:

	sub grepalize
	{
		my $list = shift;
		my $regex = shift;

		my @found = grep /$regex/, @$list;

		my %scratch = map { $_ => 1 } @list;

		delete @scratch{@found};

		@$list = keys %scratch;

		\@found
	}


	my $nfiles = grepalize \@files, qr/^car/;

	# at this point anything in $fnfiles has been
	# removed from @files.

--
Steven Lembark                               2930 W. Palmer
Workhorse Computing                       Chicago, IL 60647
                                            +1 888 359 3508