I decided to do some performance tests about reversing methods. Using Chad’s link I wrote the following methods: public static byte[] BitReverseTable = { 0x00, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0, 0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0, 0x08, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8, 0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, … Read more
& is the bitwise logical and operator – It performs the operation on 2 integer values. WHERE (sc.Attributes & 1) = 0 The above code checks to see if sc.Attributes is an even number. Which is the same as saying that the first bit is not set. Because of the name of the column though: … Read more
The bitwise operator for checking whether a flag is set in SQL is &. The WHERE clause needs to evaluate to a BOOLEAN expression, like this: create table #temp (id int, username varchar(20), flags int) insert into #temp values (1, ‘User1’, 6 /* (2 | 4) */), (2, ‘User2’, 4), (3, ‘User3’, 14 /* (2 … Read more
It is not as simple as double negation. For example, if you have x == 5, and then apply two ! operators (!!x), it will become 1 – so, it is used for normalizing boolean values in {0, 1} range. Note that you can use zero as boolean false, and non-zero for boolean true, but … Read more
inline NumericType& operator |=(NumericType& a, NumericType b) { return a= a |b; } This works? Compile and run: (Ideone) #include <iostream> using namespace std; enum class NumericType { None = 0, PadWithZero = 0x01, NegativeSign = 0x02, PositiveSign = 0x04, SpacePrefix = 0x08 }; inline NumericType operator |(NumericType a, NumericType b) { return static_cast<NumericType>(static_cast<int>(a) | … Read more
Edit: The Unsigned right-shift operator >>> is now also available in C# 11 and later. For earlier C# versions, you can use unsigned integer types, and then the << and >> do what you expect. The MSDN documentation on shift operators gives you the details. Since Java doesn’t support unsigned integers (apart from char), this … Read more
Because two’s complement bit-arithmetic makes it so Cribbed from the wikipedia page and expanded: Most Significant Bit 6 5 4 3 2 1 0 Value 0 0 0 0 0 0 1 1 3 0 0 0 0 0 0 1 0 2 0 0 0 0 0 0 0 1 1 0 0 0 … Read more
You can set the fourth bit of a number by OR-ing it with a value that is zero everywhere except in the fourth bit. This could be done as x |= (1u << 3); Similarly, you can clear the fourth bit by AND-ing it with a value that is one everywhere except in the fourth … Read more
This is underspecified. The issue of what the standard means when it refers to bit-wise operations is the subject of a few defect reports. For example defect report 1857: Additional questions about bits: The specification of the bitwise operations in 5.11 [expr.bit.and], 5.12 [expr.xor], and 5.13 [expr.or] uses the undefined term “bitwise” in describing the … Read more
Actually asm.js has not been created to write code by hand but only as result of a compilation from other languages. As far as I know there are no tools that validate the asm.js code. Have you tried to write the code in C lang and use Emscripten to generate the asm.js code? I strongly … Read more