On Wed, 9 Jul 2008 13:23:13 +0100 Andy Armstrong <[EMAIL PROTECTED]> wrote:
> On 9 Jul 2008, at 09:09, David Kaufman wrote: > > # from the POD doco at > > # > > http://search.cpan.org/~gbarr/Scalar-List-Utils-1.19/lib/List/Util.pm#DESCRIPTION > > > > $foo = first { defined($_) } @list; # first defined value in @list > > > > > > Who needs to install a CPAN module to do that? I personally would > > have > > written it as: > > > > $foo = (grep defined, @list)[0]; # first defined value in @list > > > Bear in mind that first may be much more efficient if the list is > large and/or the test is expensive Agree on the efficiency. I worked with a company on a large mod_perl application (300K+ lines of code) that used a particular function VERY often, that took an array and returned all the unique values. It did this with the common Perl Cookbook way of putting everything into a hash and returning the keys(). I switched that function to using List::MoreUtils::uniq() and they saw almost a 10% speed improvement to their entire application. Granted this was a special case because of how often that particular function was used (which was a bad design decision in the first place), but sometimes using these types of modules is useful/necessary even if the normal "Perl core" way of doing it is relatively simple. For example, if we use the technique above vs first() you get: 100 items in the list: Rate Grep first Grep 85470/s -- -74% first 331126/s 287% -- 5000 items in the list: Rate Grep first Grep 1743/s -- -99% first 125000/s 7073% -- So even for relatively small lists it can be a huge performance win. ------------------------------------------------------- Frank Wiles, Revolution Systems, LLC. Personal : [EMAIL PROTECTED] http://www.wiles.org Work : [EMAIL PROTECTED] http://www.revsys.com
