Elysian Shadows

XianForce wrote:I've seen these two operators in code here and there... but I've never been able to find their differences/specialties, nor did a google search help much. So does anyone have something to enlighten me on these two operators?

NOT:
var | returned
0    | 1
1    | 0

OR:
var1 | var2 | returned
0    | 1    | 1
0    | 0    | 0
1    | 0    | 1
1    | 1    | 1

AND:
var1 | var2 | returned
0    | 1    | 0
0    | 0    | 0
1    | 0    | 0
1    | 1    | 1

XOR:
var1 | var2 | returned
0    | 1    | 1
0    | 0    | 0
1    | 0    | 1
1    | 1    | 0

dandymcgee wrote:Has anyone discovered any neat little tricks using bit manipulation?

Is Power of 2

A non-negative binary integer value x is a power of 2 iff (x&(x-1)) is 0 using 2's complement arithmetic.

Integer Constant Multiply

Given an integer value x and an integer or floating point value y, the value of x*y can be computed efficiently using a sequence derived from the binary value of x. For example, if x is 5 (4 + 1):

y2 = y + y;
y4 = y2 + y2;
result = y + y4;

In the special case that y is an integer, this can be done with shifts:

y4 = (y << 2);
result = y + y4;

Integer Power

Given an integer value x and an integer or floating point value y, the value of y to the x power can be computed efficiently using a sequence derived from the binary value of x. For example, if x is 5 (4 + 1):

y2 = y * y;
y4 = y2 * y2;
result = y * y4;