On Tue, Jan 10, 2017 at 09:04:00AM +0100, Luca Ferrari wrote: > Hi all, > I guess it was in Modern Perl that I saw this deprecated idiom to > simulate state <http://perldoc.perl.org/functions/state.html> > variables: > > sub foo{ > my $initialized_once = 1 if 0; > ... > } > > Now, why is that working and initializing the variable the first time? > I mean, each time such row is evaluated the condition is 0 = false, so > the variable should not be initialized never. > What am I missing?
You are missing a fairly complicated interaction between the implementation details of variable handling at compile-time and run-time. The details are probably not important unless you want to understand them in order to hack on the core, or just for interest. In that case you will be able to find out all the gory details by searching the perl5-porters mailing list archives or doing some git archaeology. The behaviour came about by accident, but then people found out that it filled a hole in the language and started using it. The important point is that it was deprecated in perl-5.10.0 and will be removed in perl-5.30.0 (in a couple of years). As you note, the correct way to get this behaviour nowadays is to use the "state" keyword. -- Paul Johnson - p...@pjcj.net http://www.pjcj.net -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
