in reply to Re: Dumb, non-question: How to return 'nothing'.
in thread Dumb, non-question: How to return 'nothing'.

That's a nice solution, but is there any particular reason to use an arrayref rather than a scalarref? It'd make the iterating code just a bit cleaner:

while( my $next = $iter->() ) {
    $next = $$next;
    ...
}

[download]

As opposed to:

while( my $next = $iter->() ) {
    ($next) = @$next;
    ...
}

[download]

"There is no shame in being self-taught, only in not trying to learn in the first place." -- Atrus, Myst: The Book of D'ni.

Replies are listed 'Best First'.
Re^3: Dumb, non-question: How to return 'nothing'.
by BrowserUk (Patriarch) on Jun 17, 2011 at 20:45 UTC

    I think I've settled on requiring that the iterator be called in a list context. Eg.:

    sub i{ 
    my $n = shift; 
    return sub{ $n ? $n-- : () } 
};;

$i = i( 5 ); 
print $_ while ( $_ ) = $i->();;
5
4
3
2
1

    [download]
    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority".
    In the absence of evidence, opinion is indistinguishable from prejudice.
[reply]
[d/l]
      Would be worthwhile to add carp "Iterator not called in list context" unless wantarray; so it can't be used improperly?
[reply]
[d/l]

        Excellent notion. Thanks.

        Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
        "Science is about questioning the status quo. Questioning authority".
        In the absence of evidence, opinion is indistinguishable from prejudice.
[reply]
Re^3: Dumb, non-question: How to return 'nothing'.
by Anonymous Monk on Jun 18, 2011 at 05:16 UTC
    That's a nice solution, but is there any particular reason to use an arrayref rather than a scalarref?

    Its copy/paste from the book, the first solution -- I guess its more generic, re-usability and all that :)

[reply]

      Seeing as a scalar is always being returned, 

      while( my $next = $iter->() ) {
    ($next) = @$next;
    ...
}

      [download]

      can be shortened to 

      while( my ($next) = @{ $iter->() } ) {
    ...
}

      [download]
[reply]
[d/l]
[select]
[reply]

In Section Meditations