On Dec 6, Paul Johnson said: >On Fri, Dec 06, 2002 at 11:58:37AM -0500, Danny Miller wrote: > >> Strictly speaking, ++$count is faster than $count++. > >Strictly speaking, perl will convert $count++ to ++$count if it can.
Strictly speaking, there is another major difference no one has mentioned yet (and that many people might have trouble understanding). Using $count++ returns a NUMBER OR STRING, and then increments $count's value. ++$count increments $count's value, and returns THE SCALAR ITSELF. How does this matter? Well, watch: $i = 2; $j = ++$i / ++$i; What do you think $j will be? 3/4? Nope. 4/4, or 1. The reason is because the ++$i form is a "footnote" type of thing. Basically it means "increment $i, but leave $i here" whereas $i++ means "return $i's value, and then increment it". Want to have your mind hurt? $i = 2; @j = (++$i, ++$i, ++$i); What do you think @j will be? (5,5,5)? Yes, it will. The elements of the list ARE $i themselves, and each element's expression increments $i once; so $i becomes 5, and then the list is ($i, $i, $i), and all those are 5. (Contrast this with ($i++, $i++, $i++), where the list is (2,3,4), NOT ($i,$i,$i).) Here's the brain-hurting: $i = 2; $j = ++$i + ++$i + ++$i; What do you think $j will be? 3 + 4 + 5 = 12? No. 5 + 5 + 5 = 15? No. (NO!?) It will be 13. 4 + 4 + 5. HOW does Perl manage that? It's because ++$i isn't executed until it's reached, and the THIRD one isn't reached until the first two have been evaluated: $j = (++$i + ++$i) + ++$i; # ++$i sets $i to 3 # ++$i sets $i to 4 # ($i + $i) returns 8 # ++$i sets $i to 5 # 8 + $i returns 15 CRAZY. Or logical. Both, really. Oops. This is [EMAIL PROTECTED] Sorry. ;) -- Jeff "japhy" Pinyan [EMAIL PROTECTED] http://www.pobox.com/~japhy/ RPI Acacia brother #734 http://www.perlmonks.org/ http://www.cpan.org/ <stu> what does y/// stand for? <tenderpuss> why, yansliterate of course. [ I'm looking for programming work. If you like my work, let me know. ] -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
