in reply to Ternary operators: a hinderance, not a help

Like everything in Perl, the ternary is ripe for abuse if you want to abuse it. I used to work with a guy who wrote stuff like this: 

my $send_now_button =
  ( !$auth{SEND}
    ? ''
    :  $status != 1
       ? ''
       : $approved
         ? $send_now
           ? ''
           : qq( ...blah blah ... )
         : $send_now
           ? ''
           : ''
  );

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Yes, that's a real-life example, in production code, for a multi-million dollar corporation, although I cleaned it up a bit.

Personally, I like the ternary, as long as you don't go nuts with it. I only use it in assignments, and I don't nest them.

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Re^2: Ternary operators: a hinderance, not a help
by Zaxo (Archbishop) on Aug 09, 2005 at 19:35 UTC

    I expect that the corresponding nested if..else construct would be even more baffling. The weakness here is in the negated and chopped-up logic, not the trinary op. I'll make a first cut at rewriting it: 

    my $send_now_button =
    $auth{'SEND'} && $status==1 && $approved && !$send_now ?
    qq( ...blah blah ...) : '';

    [download]
    Not nested, you can use it now ;-)

    I think I had an easier time decyphering the (well-formatted!) nested trinary than I would have a similarly built if statement.

    Update: Just for fun, here's thing I'm slanging, formatted the best I know how, 

    my $send_now_button;
if ( !$auth{'SEND'} ) {
    $send_now_button = '';
}
else {
    if ( $status != 1 ) {
        $send_now_button = '';
    }
    else {
        if ( $approved ) {
            if ( $send_now ) {
                $send_now_button = '';
            }
            else {
                $send_now_button = qq( ...blah blah ...);
            }
        }
        else {
            if ( $send_now ) {
                $send_now_button = '';
            }
            else {
                $send_now_button = '';
            }
        }
    }
}

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    Noisy, ain't it? That maybe does even better than the trinary version at pointing out how ludicrous the logic is, but IMO trinary makes it easier to see how to fix it. I didn't even bring elsif to the table :-))

    After Compline,
    Zaxo

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Re^2: Ternary operators: a hinderance, not a help
by graff (Chancellor) on Aug 10, 2005 at 01:31 UTC
    Isn't it fun to know people like that? Such a trip!

    I wouldn't mind "wasting" a line on a default assignment in a case like that (and I often do it this way): 

    my $send_now_button = '';  # that's the default value;

$send_now_button = qq( ...blah blah ... )
    if ( $auth{SEND} and status == 1 and $approved and ! $send_now );

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