I came up with a loop using bitwise operation, resulting in a number that has every other bit turned on (i.e. in case of 8-bit, 01010101).
In theory, my loop should work just fine, and it does work fine with uint32 and uint64, but not uint8 or uint16. I wonder why...
Here's the code:
@autoreleasepool {
// a = 00000000
uint32 a = 0;
// b = 11111111
uint32 b = ~a;
// a = 11111111
a = ~a;
// if (a = 01010101) ~a = 10101010, a << 1 = 10101010
while (~a != (a << 1)) {
// 1st time: a << 1 = 11111110 = a
// 2nd time: a << 1 = 11111010 = a
a = a << 1;
// 1st time: ~a = 00000001 = a
// 2nd time: ~a = 00000101 = a
a = ~a;
// 1st time: a << 1 = 00000010 = a
// 2nd time: a << 1 = 00001010 = a
a = a << 1;
// 1st time: b ^ a = 11111101 = a
// 2nd time: b ^ a = 11110101 = a
a = b ^ a;
}
NSLog(@"%x", a);
NSLog(@"%u", b);
// Apply the same loop to a bigger scale
uint64 x = 0x0;
uint64 y = ~x;
x = ~x;
while (~x != (x << 1)) {
x = x << 1;
x = ~x;
x = x << 1;
x = y ^ x;
}
NSLog(@"%llx", x);
NSLog(@"%llu", x);
}
return 0;