[oak perl] The mysterious "undef"

Jon Seidel, CMC jseidel at edpci.com
Sat Mar 19 18:40:00 PST 2005


Sandy... One of the things that you'll use undef for is to act as a
placeholder for parameters. As I recall, there are MySql calls that often
require the use of undef, since you don't want to pass a value for, say,
parameters 2 and 3, but you have to give a value for parameters #4 and 5.

Thus, you would say something like:

$mysql->search($db, undef, undef, $text, $results)

Or something like that...if you're more familiar with the mysql interface,
feel free to correct my errors :)

...jon 

> -----Original Message-----
> From: oakland-bounces at pm.org [mailto:oakland-bounces at pm.org] 
> On Behalf Of Sandy Santra
> Sent: Friday, March 18, 2005 8:10 AM
> To: Oakland Perl
> Subject: [oak perl] The mysterious "undef"
> 
> 
> I keep seeing "undef" mentioned in the llama book.
> 
> I've tried to define a variable as not having a value, 
> theoretically being 
> "undef," but when I use the print command, I never see 
> "undef" print to my 
> screen; nothing prints at all.
> 
> I wanted to learn the different between a zero value and 
> undef because the 
> llama book keeps saying there is one.  Is this a pointless 
> issue to pursue?
> 
> Clarification greatly appreciated.  Thanks.
> 
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