Jiri has gotten some good answers. I got to work late today after working until 11:30 last night meeting my 5:00 deadline :-P
I did occur to me that a fair number of us may not completely grok bitwise stuff. That's computer science stuff, and a lot of us got here by other routes-I see a lot of C programmers doing bitwise stuff, but relatively few AS programmers (at least, we don't talk about it a lot). Still, it can be blazingly fast, so when you have a need for speed, they are great. So I thought I'd talk a little about bit operations. If you already understand them, no need to read further (unless you wish to check my accuracy). First, the basics. We all probably know this, but a byte is no more than a series of on-off switches, or bits--eight of them on most modern computers. On is represented by 1, off by 0. So, a byte with every other bit on would be 10101010. When you do a bitwise operation, you are comparing bits. The bitwise OR operator, | , compares bits. If either of them is on (1), the result is 1. If both are off (0), the result is 0. Consider the following: 120 | 96 Compares 10101010 and 01100000, giving the result 11101010 (234 decimal). Visually, this may help: 10101010 01100000 ________ 11101010 We get that result because the | operator compares each bit. If either of them is on, the result is 1 for that bit. The AND operator & is similar in that it compares bit by bit, but both bits have to be on to get a 1 result. Comparing the same two numbers as before, 120 & 96, gives you the result 00100000, or 32 decimal. 10101010 01100000 ________ 00101010 Sometimes we use these as flags, where every bit can represent a Boolean value. They also can be used for fast math operations (check out http://lab.polygonal.de/2007/05/10/bitwise-gems-fast-integer-math/ This barely scratches the surface of bitwise operators and their power, but I hope it intrigues some of you enough to pursue it further. Cordially, Kerry Thompson _______________________________________________ Flashcoders mailing list [email protected] http://chattyfig.figleaf.com/mailman/listinfo/flashcoders
