tilly once posted
something that could be coerced to do this.
Update: It would be kind of the inside-out solution to this problem, you could get a function callback for every combination of values, but I think to get an actual iterator function using this method, similar to the iterator produced by my $iter = do { my $i; sub { $i++ } };, you'd need a co-routine. Unless tilly can wrangle it out of his code :-)
There does seem to be a Coroutine Module on CPAN, might be fun to look into :)
Update: Taking the initiative, I wrangled tilly's code myself (just couldn't wait for the book :)
use strict;
use warnings;
my $iterator = mk_iter(
[1..2], ["a".."c"], [3..5]
);
while (my @arr = $iterator->()) {
print "@arr\n";
}
sub mk_iter {
my $range = shift;
my $i = 0;
my $end = @$range;
my $iter = sub {
return unless $i < $end;
return $$range[$i++];
};
@_ ? ret_iter($iter, @_) : $iter;
}
sub ret_iter {
my $iter = shift;
my $range = shift;
my $i = 0;
my $end = @$range;
my @arr;
my $new_iter = sub {
$i = 0 unless $i < $end;
return unless $i or @arr = $iter->();
return @arr, $$range[$i++];
};
@_ ? ret_iter($new_iter, @_) : $new_iter;
}
#####################################
# Update
# Here's a variation which is closer to what was
# Originally asked for, i.e. all combinations from
# 2-4 characters
use strict;
use warnings;
use strict;
use warnings;
my $iterator = make_iter(
2,4,[qw(A C G N T)]
);
while (my @arr = $iterator->()) {
print "@arr\n";
}
sub make_iter {
my ($start, $end, $range) = @_;
my $nxt_iter = sub { return };
my $iter = sub {
my @data;
unless (@data = $nxt_iter->()) {
return unless $start <= $end;
$nxt_iter = mk_iter( ($range) x $start++);
return $nxt_iter->();
};
@data;
}
}
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