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bla!! · 07-07-2005, 08:16 PM

Ok, happy hour's over

The main use I've found for these is in optimizing your own code to run faster on specific machine's.

To explicitly use them, a knowledge of Assembly is needed. They are used quite a bit to set conditional flags.

Here's a couple of neat aspects of bitwise opearators.

They can be used to zero out variables.

Code:

x      = 01101001
~x     = 10010110
x & ~x = 00000000

x & ~x will always be 0.

They can be used as an identity function

Code:

x = 01101001
y = 00111010
z = x ^ y
z = 01010011

z ^ x = 001110010 = y

So (x ^ y) ^ x = y
and (x ^ y) ^ y = x

You can implement all of the arithmetic functions using bitwise operators also, and many of them will run faster than an un-optomized version.

Also, you're probably going to learn about <<, >> and >>>. << Is the left shift operator, >> Is the logical right shift, >>> is the arithmetic right shift.

Left Shift
The arithmetic left shift takes a bit pattern and shifts it to the left the number specified after the << sign, filling the new spaces with the farthest right bit of the original number.

For example

Code:

x      = 01001011
x << 3 = 01011000

y      = 01001010
y << 3 = 01010000

Logical Right Shift

>> Is the logical right shift. This shifts a bit pattern to the right by the number following the >> sign, filling the extra bits with 0's.

For example

Code:

x      = 01001011
x >> 3 = 00001001

y      = 10110101
y >> 3 = 00010110

Arithmetic Right Shift

>>> Is the arithmetic right shift. This does the same as the logical right shift, but instead fills the extra bits with copies of the farthest left bit.

For example

Code:

x       = 01001011
x >>> 3 = 00010110

y       = 10110101
y >>> 3 = 11110110

07-07-2005, 08:16 PM	#4 (permalink)
bla!! Monster Techie Join Date: May 2004 Location: /usr/root/mn/us Posts: 1,121	Ok, happy hour's over The main use I've found for these is in optimizing your own code to run faster on specific machine's. To explicitly use them, a knowledge of Assembly is needed. They are used quite a bit to set conditional flags. Here's a couple of neat aspects of bitwise opearators. They can be used to zero out variables. Code: x = 01101001 ~x = 10010110 x & ~x = 00000000 x & ~x will always be 0. They can be used as an identity function Code: x = 01101001 y = 00111010 z = x ^ y z = 01010011 z ^ x = 001110010 = y So (x ^ y) ^ x = y and (x ^ y) ^ y = x You can implement all of the arithmetic functions using bitwise operators also, and many of them will run faster than an un-optomized version. Also, you're probably going to learn about <<, >> and >>>. << Is the left shift operator, >> Is the logical right shift, >>> is the arithmetic right shift. Left Shift The arithmetic left shift takes a bit pattern and shifts it to the left the number specified after the << sign, filling the new spaces with the farthest right bit of the original number. For example Code: x = 01001011 x << 3 = 01011000 y = 01001010 y << 3 = 01010000 Logical Right Shift >> Is the logical right shift. This shifts a bit pattern to the right by the number following the >> sign, filling the extra bits with 0's. For example Code: x = 01001011 x >> 3 = 00001001 y = 10110101 y >> 3 = 00010110 Arithmetic Right Shift >>> Is the arithmetic right shift. This does the same as the logical right shift, but instead fills the extra bits with copies of the farthest left bit. For example Code: x = 01001011 x >>> 3 = 00010110 y = 10110101 y >>> 3 = 11110110 __________________ <br> Its a frigging Laptop, not a Labtop!!!!