Hi hw! Please see http://www.shlomifish.org/philosophy/computers/netiquette/email/reply-to-list.html .
On Sat, 1 Jul 2017 19:15:22 +0200 hw <h...@gc-24.de> wrote: > Shlomi Fish wrote: > > Hi Shawn! > > > > On Sat, 1 Jul 2017 11:32:30 -0400 > > Shawn H Corey <shawnhco...@gmail.com> wrote: > > > >> On Sat, 1 Jul 2017 17:27:02 +0200 > >> hw <h...@gc-24.de> wrote: > >> > >>> > >>> Hi, > >>> > >>> can someone please explain this: > >>> > >>> > >>> perl -e 'my $i = 0; $i = defined($i) ? (!!$i) : 0; print "i: $i\n";' > >>> i: > >>> > >>> > >>> Particularly: > >>> > >>> > >>> + Why doesn´t it print 1? > >> > >> Because !!$i is zero > >> > >>> > >>> + How is this not a bug? > >> > >> Nope, no bug. > >> > >>> > >>> + What is being printed here? > >> > >> !!$i which is !(!(0)) which is !(1) which is 0 > >> > > > > I suspect !1 returns an empty string in scalar context. > > What would be the reasoning for a numerical operator turning > numerical values into (empty) strings within a numerical context? > "!" is not a numerical operator - it is a *logical* operator. If one passes a true value to it one gets a false value. Else, one gets a true value. See http://perldoc.perl.org/perlop.html . If used in a numerical context, false values are treated as zeroes, but not all of them are zeroes in other contexts. Regards, Shlomi > > > > > >>> > >>> + How do you do what I intended in perl? > >>> > >> > >> How do we know what you intend? > >> > >> > > > > > > > -- ----------------------------------------------------------------- Shlomi Fish http://www.shlomifish.org/ UNIX Fortune Cookies - http://www.shlomifish.org/humour/fortunes/ Real programmers don’t write workarounds. They tell their users to upgrade their software. — http://www.shlomifish.org/humour.html Please reply to list if it's a mailing list post - http://shlom.in/reply . -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
