Re: Refactoring: dumb or witty use of ternary operator?

Or am I overseeing some "important" side effect?

Probably a warnings freak like me :) ~~If the the value of $outhash{$str} is undefined, you'll get a warning about using an undefined value.~~ update - you won't but I bet your colleague assumed the same thing that I did :)

My guess is that the keys aren't known until the script is run, and that's your colleague's way of getting rid of the warnings. A perfectly valid way too. They are making you explicitly aware of the fact that $outhash{$str} may be undefined when you try to increment it.

This would work equally well:

$outhash{$str}||=0;
$outhash{$str}++;
[download]

.02

cLive ;-)

Comment on Re: Refactoring: dumb or witty use of ternary operator? Download Code

Replies are listed 'Best First'.
Re: Refactoring: dumb or witty use of ternary operator? by Abigail-II (Bishop) on Jun 22, 2004 at 10:06 UTC
If the the value of $outhash{$str} is undefined, you'll get a warning about using an undefined value. Are you sure about that? Can you show code giving the warning? If you can construct code that generates a warning when ++ is applied to an undefined value, make sure to report it as a bug, because that's not supposed to happen. This would work equally well: `$outhash {$str} \|\|= 0; $outhash {$str} ++;` [download] Yeah, but why bother? From the documentation about auto-increment and auto-decrement: `"undef" is always treated as numeric, and in particular is changed to 0 before incrementing (so that a post-increment of an undef value will return 0 rather than "undef").` [download] Abigail	[reply] [d/l] [select]
Re^2: Refactoring: dumb or witty use of ternary operator? by cLive ;-) (Prior) on Jun 22, 2004 at 17:54 UTC
"Are you sure about that?". No, obviously, but my guess is that his colleague made the same assumption that I did :) cLive ;-)	[reply]
Re^2: Refactoring: dumb or witty use of ternary operator? by diotalevi (Canon) on Jun 22, 2004 at 18:32 UTC
If that were a check for an undef value, it should have used the defined() test which is instructive to us when trying to understand the code.	[reply]
Re^2: Refactoring: dumb or witty use of ternary operator? by PetaMem (Priest) on Jun 22, 2004 at 06:54 UTC
If the the value of $outhash{$str} is undefined, you'll get a warning about using an undefined value. This was my first thought too, but then the plain mentioning of $outhash{$str} in the ternary operator test section should do also - shouldn't it? Bye PetaMem All Perl: MT, NLP, NLU	[reply]
Re^3: Refactoring: dumb or witty use of ternary operator? by cLive ;-) (Prior) on Jun 22, 2004 at 08:12 UTC
Try this: `#!/usr/bin/perl use strict; use warnings; my $x; $x = $x+1; print $x;` [download] I get: `Use of uninitialized value in addition (+) at tmp.pl line 6.` [download] Then try: `#!/usr/bin/perl use strict; use warnings; my $x; $x = $x ? $x+1 : 1; print $x;` [download] to see the difference... cLive ;-)	[reply] [d/l] [select]
Re^3: Refactoring: dumb or witty use of ternary operator? by revdiablo (Prior) on Jun 22, 2004 at 07:07 UTC
Neither methods generate a warning for me, using perl 5.8.4. `$ perl -wle '$outhash{$ARGV[0]}++; print $outhash{$ARGV[0]}' foo 1 $ perl -wle '$outhash{$ARGV[0]} ? ($outhash{$ARGV[0]}++) : ($outhash{$ARGV[0]} = 1); print $outhash{$ARGV[0]}' foo 1 $` [download]	[reply] [d/l]