private double always returning 0

Question

I have this function:

 private double getTotal(string str)
    {
        double total = 0;
        byte[] asciiBytes = Encoding.ASCII.GetBytes(str);

        foreach(int c in asciiBytes)
        {
            total = total + c;
            total = total * (5 * (c ^ 2) / (c*6));
        }
        return Math.Round(total);
    }

This is used to get a total of a strings ASCII values but does some math along the way rather than just adding. I need this to return the total, but is currently returning 0. How can I make it return the correct value? (PS: It needs to return an integer, but this can be in the datatype of a double for conversion later. Basically just need it to return a whole number.) (PSPS: I don't know what the string will be, it's up to the end user)

_

Answer 1

You probably misunderstood the ^ sign. It stands for a bitwise exclusive or, rather than an exponentiation. If you want to use the latter, use this:

total = total * (5 * (Math.Pow (c, 2) / (c * 6));

However, you could write it shorter/more beautiful/more efficient as well:

total *= (5 * (c * c) / (6 * c));

I replaced the Pow, as it is slower than a simple multiplication and used an assignment-operator.

Furthermore, the equation itself can be simplified:

total *= c * (5 / 6);

However, you should still mark the numbers as doubles, as 5/6 would result in 0 otherwise:

total *= c * (5.0 / 6.0)

For more information on exponentiation in C#, have a look at this.

---

By the way, the ^ sign takes every bit of the numbers and compares them. The new value will be 1 if the first bit or the second bit, but not both bits are 1.

So for example 0101 xor 1110 would result in 1011.

Answer 2

You have casting problem. The c variable is integer. Your problem is in the total = total * (5 * (c ^ 2) / (c*6)); expression.

Because the internal results (c ^ 2) and (c*6) aren't double, when the division result has floating point such as 0.nnnnn, the final result isn't double and you get only the 0 which is the real part of the number. And the result expression (5 * (c ^ 2) / (c*6)) as an Integer is 0. Finally the expression is as total=total * (0);

Use internal castings in your code Replace your code with the following :

total = total * (5 * ((double)(c ^ 2)) / ((double)(c * 6)));

Please run the following code

    static private double getTotal(string str)
    {
        double total = 0;
        byte[] asciiBytes = Encoding.ASCII.GetBytes(str);

        foreach (int c in asciiBytes)
        {
            double dC = c;
            total = total + c;
            double cXor2 = c ^ 2;
            double c6 = c * 6;
            double fiveCXor2 = 5 * cXor2;
            double semiFinal = fiveCXor2 / c6;
            double final = total * semiFinal;

            Console.WriteLine("c = " + (c).ToString());
            Console.WriteLine("c ^ 2 = " + (cXor2).ToString());
            Console.WriteLine("c * 6 = " + (c6).ToString());
            Console.WriteLine("5 * (c ^ 2) = " + (fiveCXor2).ToString());
            Console.WriteLine("semi final = " + semiFinal);
            Console.WriteLine("final = " + final);
            Console.WriteLine("--------------------------------------------");
            total = total * (5 * (c ^ 2) / (c * 6));
            Console.WriteLine("TOTAL = " + total);
            Console.WriteLine("--------------------------------------------");
        }
        return Math.Round(total);
    }

Sample result is :

c = 97
c ^ 2 = 99
c * 6 = 582
5 * (c ^ 2) = 495
semi final = 0.850515463917526
final = 82.5
--------------------------------------------
TOTAL = 0
--------------------------------------------
c = 98
c ^ 2 = 96
c * 6 = 588
5 * (c ^ 2) = 480
semi final = 0.816326530612245
final = 80
--------------------------------------------
TOTAL = 0
--------------------------------------------

As you can see the problem is casting

Because the c variable is int the casting procedure is :

step 1
[double] = [double] * ([int] * ([int] ^ [int] ) / ([int] * [int] )) 
total    = total    * (5     * (c     ^ 2     ) / (c     * 6     ));

step 2
[double] = [double] * ([int] * ([int]) / ([int] )) 
total    = total    * (5     * (X)     / (Y)    );

step 3
[double] = [double] * ([int] * [int])) 
total    = total    * (5     * XdivY    );
**CASTING PROBLEM : In this step the XdivY is integer and when the result is 0.1234 the INT     result is 0**

step 4
[double] = [double] * ([double])) 
total    = total    * (5mulXdivY    );    
here c# casting the 5mulXdivY  0  to double but the result is zero

step 5
[double] = [double] 
total    = 0

Answer 3

Problem is with the this line in your code

total = total * (5 * (c ^ 2) / (c*6));

c ^ 2 returns a smaller value than c*6. Now the operator / is integer division so the result of a smallnumber/largenumber will always return zero. This will make the value of variable total zero in every iteration of the loop. Change the code like this and it will give you the result you expect.

private double getTotal(string str)
        {
            double total = 0;
            byte[] asciiBytes = Encoding.ASCII.GetBytes(str);

            foreach (int c in asciiBytes)
            {
                total = total + c;
                total = total * (5 * (double)(c ^ 2) / (double)(c * 6));
            }
            return Math.Round(total);
        }

Hope it helps.

Answer 4

Add double to one of the ints

private double getTotal(string str)
        {
            double total = 0;
            byte[] asciiBytes = Encoding.ASCII.GetBytes(str);

            foreach (int c in asciiBytes)
            {
                total = total + c;
                total = total * ((double)5 * (c ^ 2) / (c * 6));
            }
            return Math.Round(total);
        }