Just an example of building an iterator with a closure to walk
through multiple arrays in parallel (maybe you have a table (2d
array) and want to walk the columns). This is just a simple one that
runs through the arrays and then resets so it can be used again:
sub parallel_it {
my @arr_refs = @_;
my $iter = 0;
return sub {
my @return = map{$_->[$iter]}@arr_refs;
$iter++;
return @return if grep{defined $_}@return;
$iter = 0;
return;
};
};
my @one = (0, 1, 2, 3, 4, 5, 6);
my @two = qw/Sun Mon Tue Wed Thu Fri Sat/;
my @three = qw/Zeroday Oneday Twoday Threeday
Fourday Fiveday Sixday/;
my $triples = parallel_it( \(@one,@two,@three) );
while( my($a, $b, $c) = $triples->() ){
print "$a:$b:$c\n";
}
# update @one and go again
@one = qw/A B C D E F G/;
while( my($a, $b, $c) = $triples->() ){
print "$a:$b:$c\n";
}
my @table = ( [ 1, undef, 3, 4],
[ 6, 7,],
[qw/a b c d e f/],
);
my $columns = parallel_it(@table);
while( my @col = $columns->() ){
print join(',', map{ $_ ? $_ : ' ' } @col),"\n";
}
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