Re: Little annoying mistakes ... of others

in reply to Little annoying mistakes ... of others

A pretty common logic error is forgetting to explicitly check all expected values against the variable:

use strict;
use warnings;

my $foo = 'boo';
if ($foo eq 'goo' || 'moo') {
    print "$foo\n";
}
[download]

when this is really desired:

if ($foo eq 'goo' || $foo eq 'moo') {
[download]

Obviously, this is not unique to Perl, but I do see it quite often.

Comment on Re: Little annoying mistakes ... of others Select or Download Code

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Re^2: Little annoying mistakes ... of others by jeffa (Bishop) on Dec 07, 2008 at 16:06 UTC
Actually ... i would desire this: `use strict; use warnings; my $arg = shift \|\| 'boo'; my @valid = qw( goo moo foo voo doo poo ); print "$arg matches\n" if grep /$arg/, @valid;` [download] But this bring up an annoyance as well, because this mistake will compile and always return true (as long as the array being checked is not empty): `# wrong way ahead! print "$arg matches\n" if grep $arg, @valid;` [download] Oops! jeffa L-LL-L--L-LL-L--L-LL-L-- -R--R-RR-R--R-RR-R--R-RR B--B--B--B--B--B--B--B-- H---H---H---H---H---H--- (the triplet paradiddle with high-hat)	[reply] [d/l] [select]
Re^3: Little annoying mistakes ... of others by szabgab (Priest) on Dec 28, 2008 at 19:26 UTC
Wow, I am writing down the examples as test cases but I can't figure out why is the second example always true? could you please explain?	[reply]
Re^4: Little annoying mistakes ... of others by jeffa (Bishop) on Dec 29, 2008 at 14:16 UTC
I think this: `print "$arg matches\n" if grep $arg, @valid;` [download] Is equivalent to this: `print "$arg matches\n" if grep { $arg } @valid;` [download] So as long as @valid and $arg are not false, then the match will also be true. (If $arg is 0 (zero) then the second example will not always be true.) jeffa L-LL-L--L-LL-L--L-LL-L-- -R--R-RR-R--R-RR-R--R-RR B--B--B--B--B--B--B--B-- H---H---H---H---H---H--- (the triplet paradiddle with high-hat)	[reply] [d/l] [select]
Re^2: Little annoying mistakes ... of others by szabgab (Priest) on Dec 07, 2008 at 04:39 UTC
This is exactly the type of examples I am looking for. Funny as I have just seen this happen in my last class 4 days ago.	[reply]
Re^2: Little annoying mistakes ... of others by parv (Parson) on Dec 07, 2008 at 11:44 UTC
`if ($foo eq 'goo' \|\| 'moo') { ... }` Error that may be but I do wish somethimes that that ought to be correct.	[reply] [d/l]
Re^3: Little annoying mistakes ... of others by szabgab (Priest) on Dec 10, 2008 at 07:03 UTC
goto Perl 6;	[reply]

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