and tests whether both expressions are logically True while & (when used with True/False values) tests if both are True. In Python, empty built-in objects are typically treated as logically False while non-empty built-ins are logically True. This facilitates the common use case where you want to do something if a list is empty and … Read more
The XOR operation (x ^ 0x1) inverts bit 0. So the expression effectively means: if bit 0 of x is 0, or any other bit of x is 1, then the expression is true. Conversely the expression is false if x == 1. So the test is the same as: if (x != 1) and … Read more
In Java, it means nothing. But that comment says that the line is specifically for GWT, which is a way to compile Java to JavaScript. In JavaScript, integers are kind of like doubles-that-act-as-integers. They have a max value of 2^53, for instance. But bitwise operators treat numbers as if they’re 32-bit, which is exactly what … Read more
I have a sneaking suspicion you got this code from the same book I’m reading…The code itself here isn’t nearly as cryptic as the the operators- |=, &, and << which aren’t normally used by us layman- the author didn’t bother taking the extra time out in explaining the process nor what the actual mechanics … Read more
The RFC is just trying to say that a signed integer is a normal 4-byte integer with bytes ordered in a big-endian way. Now, you are most probably working on a little-endian machine and BitConverter.GetBytes() will give you the byte[] reversed. So you could try: int intValue; byte[] intBytes = BitConverter.GetBytes(intValue); Array.Reverse(intBytes); byte[] result = … Read more
I did some more work on these extensions – You can find the code here I wrote some extension methods that extend System.Enum that I use often… I’m not claiming that they are bulletproof, but they have helped… Comments removed… namespace Enum.Extensions { public static class EnumerationExtensions { public static bool Has<T>(this System.Enum type, T … Read more
~ is a bitwise operator that flips all bits in its operand. For example, if your number was 1, its binary representation of the IEEE 754 float (how JavaScript treats numbers) would be… 0011 1111 1111 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 So ~ converts its operand to … Read more
How does it work? Our theory was that using such an operator casts the number to an integer, thus removing the fractional part All bitwise operations except unsigned right shift, >>>, work on signed 32-bit integers. So using bitwise operations will convert a float to an integer. Does it have any advantages over doing Math.floor? … Read more
Check the Bit Twiddling Hacks. You need to get the base 2 logarithm, then add 1 to that. Example for a 32-bit value: Round up to the next highest power of 2 unsigned int v; // compute the next highest power of 2 of 32-bit v v–; v |= v >> 1; v |= v … Read more
NOTE: All algorithms below are in C, but should be portable to your language of choice (just don’t look at me when they’re not as fast 🙂 Options Low Memory (32-bit int, 32-bit machine)(from here): unsigned int reverse(register unsigned int x) { x = (((x & 0xaaaaaaaa) >> 1) | ((x & 0x55555555) << 1)); … Read more