Re: Whacky increment/assignment logic with $foo++ vs ++$foo

On Tue, Oct 6, 2009 at 10:28 AM, Paul M Foster <paulf@quillandmouse.com>wrote: > On Tue, Oct 06, 2009 at 08:51:17AM -0400, Bob McConnell wrote: > > > From: Joost [mailto:joost.t.hart@planet.nl] > > > "Daevid Vincent" wrote: > > >>> From: Ben Dunlap [mailto:bdunlap@agentintellect.com] > > > > > $a = $a++; > > > > I just think this is an ambiguous line of code that wasn't thought > > through. The presence of the postfix operator makes the result > > undefined, no matter what language you are using. It will be an accident > > if you get the results you are expecting. > > The behavior of the ++ operator is the invention of Kernighan and Ritchie. > I don't imagine they ever foresaw anyone doing something as silly as > > a = a++; > > except under the rarest of circumstances. > > Paul > > -- > Paul M. Foster > > -- > PHP General Mailing List (http://www.php.net/) > To unsubscribe, visit: http://www.php.net/unsub.php > > No matter how silly it can looks like (a = a++) it is still completely valid code and it SHOULD run without problems. If we analyse any portion of code (like a simple assigment) out of context it'll always looks like this, just silly (in this case it's really really silly). One point here, that nobody mention, is the side effect. ++$i has a totaly different side effect than $i++ Sometimes you don't need the side effect but in other situations it really matter. Does these behaves exactly? for($i=0; $i<10; ++$i) for($i=0; $i<10; $i++) There is no side effect on the incremental section because the result is not evaluated. and what about these? $array[ $index++ ] = $elem; $array[ ++$index ] = $elem; You can read more about the side effect at http://en.wikipedia.org/wiki/Side_effect_%28computer_science%29 -- Martin Scotta