On Tue, Dec 29, 2009 at 8:27 PM, Steve Bertrand <st...@ibctech.ca> wrote:
> Happy holidays everyone!
>
> I've found Devel::Cover to be an exceptionally handy item, but don't
> think I entirely grasp what the term 'short-circuiting' actually means.
>
I'm not familiar with Devel::Cover. The phrase "short circuit" usually
refers to the boolean operators && and ||. Perl stops evaluating boolean
operations as soon as it can. For example, take this code:
if ($true || $false) { print "True\n"; }
The || operator evaluates as true whenever at least one condition evaluates
true. Perl grabs the left hand side: $true. It sees a true value and prints
the line. Perl never looks at $false because the value of $false doesn't
matter.
Now consider this example:
if (do_first(1, 2) || do_second(\$result)) { print "True\n"; }
Assume do_first returns true and the line prints. What about $result? Perl
never called into the code for do_second, and $result never changed. We say
that Perl short circuited the evaluation. It stopped executing code as soon
as it knew the outcome of the logic statement.
--
Robert Wohlfarth
