isnt something like:
$data eq "8000" or $data eq "0080" the same as: $data eq "8000" || $data eq "0080";
A little experimentation should reveal that Perl thinks it is:
c:\@Work\Perl>perl -wMstrict -MO=Deparse,-p -le "my $data = '8000'; ;; if ($data eq '8000' or $data eq '0080') { print 'yes 1'; }; if ($data eq '8000' || $data eq '0080') { print 'yes 2'; }; " BEGIN { $^W = 1; } BEGIN { $/ = "\n"; $\ = "\n"; } use strict 'refs'; (my $data = '8000'); if ((($data eq '8000') or ($data eq '0080'))) { print('yes 1'); } if ((($data eq '8000') or ($data eq '0080'))) { print('yes 2'); } -e syntax OK
... i have ... tried ... swapping the 8A-8F/A0 with eq to no avail.
Again with the experimentation:
I don't know what code you tried when you used eq (the proper comparator for strings), but clearly it should work. At the same time, I would also agree with other respondents that a re-organization of the code to avoid an eye- and mind-bezoggling onslaught of if-statements would be very valuable just for the great increase in readability and maintainability I would expect it to yield.c:\@Work\Perl>perl -wMstrict -le "my $data = '8000'; ;; if ($data eq '8000' or $data eq '0080') { print 'yes 1'; }; if ($data eq '8000' || $data eq '0080') { print 'yes 2'; }; " yes 1 yes 2
i thought i read somewhere that its was better to use "||" instead of "or" and use "&&" instead of "and".
The problem with and and or is that these logical operators have such low precedence: their precedence is lower than , (comma), i.e., lower than whale dung. This was done so that a statement like
open my $fh, '<', $filename or die "opening '$filename': $!";
would work as expected. Unfortunately, such low precedence has some surprising side-effects, hence && and || are recommended for 'normal' usage, a recommendation I would endorse since I've stumbled over these odd side-effects myself.
Update: Here's an example of a precedence-induced difference between ! and not. This code produces warnings, but you may not be so lucky.
c:\@Work\Perl>perl -wMstrict -MData::Dump -le "my ($x, $y) = (4, 5); ;; my @ra = (1, 2, ! 3, $x, $y); dd \@ra; ;; my @rb = (1, 2, not 3, $x, $y); dd \@rb; ;; print qq{but \$x and \$y are still $x and $y}; " Useless use of a constant (3) in void context at -e line 1. Useless use of private variable in void context at -e line 1. [1, 2, "", 4, 5] [1, 2, ""] but $x and $y are still 4 and 5
In reply to Re^3: perl unpack and matching the unpacked data
by AnomalousMonk
in thread perl unpack and matching the unpacked data
by james28909
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