Re: Re: (Perl6) Groking Continuations (iterators)

in reply to Re: (Perl6) Groking Continuations (iterators)
in thread (Perl6) Groking Continuations

Or you use closures to turn call-backs into iterators. Here I've altered the API a smidge because the original code used chdir() during the loop which is probably an unexpected side-effect. For anyone that is interested - Dominus is writing an excellent book on iterators and it includes a section on transforming recursive calls somewhat thusly. Here's a link to the book's web page (which you must all now go out and buy (when it is published)).

BTW - this doesn't explain continuations at all - I'm just presenting a different perl5-accessible solution to the problem that tye posed.


my $find = find('', '');
while (my $file = $find->()) {
    print join('/', @$file)."\n";
}

sub find {
    my @todo = shift;
    my @results;
    return sub {
        while (@todo and not @results) {
            my $subdir  = shift @todo;
            $subdir = "."  if  ! defined $subdir or $subdir eq '';
            $subdir .= "/"  if $subdir =~ m{[^/]$};
            my @files= ( glob("$subdir.*"), glob("$subdir*") );
            for my $file (  @files  ) {
                next   if  $file =~ /\.\.?$/;
                if(  ! -l $file   &&  -d _  ) {
                    push @todo, \ $file;
                }
                push @results, [ $subdir, substr($file,length($subdir)
+) ];
            }
        }
        return shift @results;
    };
}
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