in reply to syntax of defined

In Perl 5 you need parenthesis directly after the 'if', and curlies both after if and else: 

if (defined param('end_date')) {
   ...
} else {
   ...
}

[download]

see perlintro, perlsyn.

(In Perl 6 you can omit the parenthesis)

Replies are listed 'Best First'.
Re^2: syntax of defined
by ikegami (Patriarch) on Mar 09, 2010 at 23:00 UTC

    In Perl 5 you need parenthesis directly after the 'if',

    Except if you use the if statement modifier 

    bar() if foo();

    [download]

    Mind you, the statement modifier wouldn't be useful here. The condition operator, on the other hand, would be useful. 

    $user_input->{end_date} = defined(param('end_date'))
    ? param('end_date')
    : param('start_date');

    [download]

    Mind you, param('end_date') can still be called twice for nothing. The following doesn't: 

    $user_input->{end_date} = param('end_date');
$user_input->{end_date} = param('start_date')
    if !defined($user_input->{end_date});

    [download]
    Since 5.10, the above can be simplified to the following: 
    $user_input->{end_date} = param('end_date') // param('start_date');

    [download]
    The following isn't strictly equivalent, but should do the trick if you want something similar while still supporting earlier versions of Perl: 
    $user_input->{end_date} = param('end_date') || param('start_date');

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

In Section Seekers of Perl Wisdom