C＃运算符作为函数

Question

Is there a way to use operators as functions without declaring them manually?

Func<bool, bool> not = x => !x;

Similar to (+) / (-) in Haskell. Would be handy in various LINQ scenarios involving conditional query construction. Maybe some C# (4.0+) trick I don't know about.

Edit: here is a sample to clarify what I mean:

 int MyWhere(Func<bool, bool, bool> cond) {}

a usual call would be:

MyWhere((x,y) => x && y)

a cool call would be (assuming Haskell style):

MyWhere((&&))

Answer 1

No.

You can find the definitions (F12 in VS) for the operators you can overload, and there exists a

 // struct Double
 public static bool operator ==(double left, double right);

But there is no way to call Double.operator==(a, b) .

The Framework does offer a a.Equals(b) for this particualr case, but there is no a.Add(b) .

Answer 2

For documentary purposes: user-defined operator are functions, however the C# language explicitly prohibits explicit calls (don't know the rationale). Eg:

public class X
{
    public static X operator+(X a, X b)
    {
        return new X();
    }
}

public class Program
{
    public static void Main(string[] args)
    {
        var q = new X() + new X();
        X.op_Addition(q,q); // error CS0571: 
        //   `Program.X.operator +(Program.X, Program.X)': cannot explicitly
        //   call operator or accessor
    }
}

If you were writing IL, you'd write this:

newobj instance void class X::'.ctor'()
newobj instance void class X::'.ctor'()
call class X class X::op_Addition(class X, class X)
stloc.0 

Answer 3

If i understand what you are want to do right, you can use System.Reflection and Delegate.CreateDelegate to create a delegate to the operator method.

Of course i never testet it, but operator methods are methods so it should work. This could also be automated ( To save time compared to the straight forward method ).

See:

http://msdn.microsoft.com/de-de/library/53cz7sc6.aspx