Re: strange boolean algebra behaviour

Replies are listed 'Best First'.
Re^2: strange boolean algebra behaviour by vlad_tepesch (Acolyte) on Apr 04, 2012 at 10:25 UTC
aarrrgghh!!! I could smash my head on table. operator precedence is a thing that i should have remember. I was utterly convinced that '&&' and 'and' are synonyms. Thank you.	[reply]
Re^3: strange boolean algebra behaviour by Anonymous Monk on Apr 04, 2012 at 19:27 UTC
I could smash my head on table. Don't do that, that could hurt. But if you do do it, make/post a video	[reply]
Re^2: strange boolean algebra behaviour by remiah (Hermit) on Apr 05, 2012 at 05:27 UTC
`use strict; use warnings; my $a = 1; my $b = 0; my $c = $a and $b; print "c=$c\n";` [download] This gives me warning that "Useless use of private variable in void context at tmp16.pl line 6.". line 6 is "my $c = $a and $b;". I first tried -MO=Deparse. `C:\temp>perl -MO=Deparse tmp16.pl Useless use of private variable in void context at tmp16.pl line 6. use warnings; use strict 'refs'; my $a = 1; my $b = 0; $b if my $c = $a; print "c=$c\n"; $a = 1; $b = 0; $c = $a && $b; print "c=$c\n"; tmp16.pl syntax OK` [download] So, Deparse maybe says $b of "$b if my $c = $a;" is the useless use of private variable. regards.	[reply] [d/l] [select]
Re^3: strange boolean algebra behaviour by Anonymous Monk on Apr 05, 2012 at 06:54 UTC
-p `$ perl -MO=Deparse -e " my $foo = $bar and $baz; " $baz if my $foo = $bar; -e syntax OK $ perl -MO=Deparse,-p -e " my $foo = $bar and $baz; " ((my $foo = $bar) and $baz); -e syntax OK` [download]	[reply] [d/l]
Re^4: strange boolean algebra behaviour by remiah (Hermit) on Apr 05, 2012 at 15:21 UTC
When you use the -p option, the output also includes parentheses even when they are not required by precedence, which can make it easy to see if perl is parsing your expressions the way you intended. thank you. maybe easier to see. `perl -MO=Deparse,-p -anle "print $F[3];" tmp.txt` [download] This showed me what is -a,n,l.	[reply] [d/l]