AnswerAdder.cs

// Implements addition using bit operations (an adder)
// This was an answer to a playful Koan test for .Net Core.
// I resolved not to use google and work it out from basic
// boolean math principles. Could probably be simpler, but was
// a fun exercise.

        public void AdditionWithoutPlusOrMinusOperator()
        {
            var adder = new Func<int,int,int>((a,b)=>{
                int c = 0; // carry
                int s = 0; // sum
                int t = 0; // total
                int tmp = 0;
                int w = 256; // width (2^8 in this case)

                while ((w >>= 1) > 0)
                {
                    s = (a & 1) ^ (b & 1) ^ c; 
                    tmp = (a & 1) | ((b & 1) & c); 
                    c =  tmp & (~tmp  | ((b & 1) | c)); 
                    a >>= 1;
                    b >>= 1;
                    t = (t >> 1) | (s << 7);
                }
                return t;
            });

            //Here goes your implementation to set value to FILL_ME_IN
            Assert.Equal(255,adder(200,55));
        }