flotsan wrote:
> Hey guys,
Hello,
> I am reading the Perl Camel book - Programming Perl 3rd Ed and having a bit
> of trouble to understand some of the ideas presented in section 2.11.2.
> Specifically it is told the following two statements are different:
>
> 1) if ($_ = <STDIN>) { print; } # suboptimal: doesn't test
> defined
> 2) if (defined($_ = <STDIN>)) { print; } # best
>
> But as I see it, these two do the same thing in that in the #1 one, the $_ =
> <STDIN> expression returns an lvalue $_ which is then evaluated in the
> boolean context provided by the "if" operator. Then it follows if $_ has the
> "undef" value, then it would produce a "false" in the boolean context which
> is conceptually the same as the 2nd expression.
>
> Is there anything wrong in my understanding that somebody can straighten me
> out?
Yes, Perl has five "false" values: undef, (), 0, '' and '0', and two of those
are valid input from the readline operator.
John
--
use Perl;
program
fulfillment
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
<http://learn.perl.org/> <http://learn.perl.org/first-response>
