Comments on: For Vs. While

By: jackson

jackson — Mon, 30 Nov 2009 18:00:42 +0000

Thanks for the points!

1. Yes, I think they’re wrong. :) If you look at the bytecodes available in AVM2 you’ll see instructions like “increment_i”, “inclocal_i”, “add_i” and so forth. Adobe puts out a good overview. There’s no mention of “pre” and “post”; that is only an order of bytecode generation by the compiler based on the precedence rules of AS3. In the end it is the same bytecode. Still, that’s something I could have been clearer about in the article.

2. My tests didn’t show any difference between “forward while” and “forward for” for AS3. Do you see any difference when you don’t swap the order around? How about when you use Flex instead of CS4? I’m not seeing any difference when I swap any of the tests around.

3. This is good to know! I wonder what accounts for the mysterious slowness “forward for” on AS2…

By: Robert Penner

Robert Penner — Mon, 30 Nov 2009 17:38:26 +0000

A few points:
1. Some people say there is a speed difference between pre-increment and post-increment.

2. When I move the “forward while” code to the top, it runs slower than the “forward for” (AS3, Flash CS4). It often seems that code running first has a disadvantage.

3. I decompiled the loops; the for and while loops come back exactly the same (AS2 and AS3).

By: jackson

jackson — Fri, 27 Nov 2009 18:43:36 +0000

That's the meaning of syntax sugar. Repeated testing (above) shows that this is, quite unfortunately, not the case.

By: Tommy Kjær Andersen

Tommy Kjær Andersen — Fri, 27 Nov 2009 09:49:55 +0000

if i remember rigth the for loops are converted to while loops by the compiler, so the results souldt be the same.