What is the purpose of this tilde in C#

Question

I'm trying to port this C# code:

public static ulong WILDCARD_COLLISION_TYPE
{
    get
    {
        int parse = ~0;
        return (ulong)parse;
    }
}

If I understand correctly, doesn't the ~ symbol perform a bitwise complement so what is the point of doing ~0? and then returning it?

This will return a numeric value composed of 64 bits all set that could be used as a bit mask to test some kind of flag — Steve, Feb 20 '16 at 13:37
It's equivalent of combersome `int parsed = unchecked((int) 0xFFFFFFFF);` you can put it just as `return 0xFFFFFFFFUL;` but it's easy to *miscount* the `F`s — Dmitry Bychenko, Feb 20 '16 at 13:46

score 8 · Accepted Answer · edited Jul 07 '16 at 11:28

From the ~ Operator documentation:

The ~ operator performs a bitwise complement operation on its operand, which has the effect of reversing each bit. Bitwise complement operators are predefined for int, uint, long, and ulong.

For example:

unsigned int i = ~0;

Result: Max number I can assign to i

and

signed int y = ~0;

Result: -1

so fore more info we can say that ~0 is just an int with all bits set to 1. When interpreted as unsigned this will be equivalent to UINT_MAX. When interpreted as signed this will be -1

What is the purpose of this tilde in C#

1 Answers1