[C#] Get only the first 10 number of a X lenght digit.

Question

Hello all. I have a method , that calculates distance between two xyz cords, and return me a nice long double number like 10,12345678963235. But I only need 10,12345 , that would be enought for me. How can I do this? This is the method that returns me the value:

public static double Distance(Vector3 v1, Vector3 v2)
{        
    return
    (
        Math.Sqrt
        (
            (v1.X - v2.X) * (v1.X - v2.X) +
            (v1.Y - v2.Y) * (v1.Y - v2.Y) +
            (v1.Z - v2.Z) * (v1.Z - v2.Z)
        )
    );
}

Thank you!

Answer 1

After re-reading the question, I think the only option you have is to convert to a string, take the first 10 characters, then convert back to double.

If your number is a decimal (you've got a , not a . so I'm not sure) the method below should work, otherwise you'll need to do the string thing.

---

Math.Round(
    Math.Sqrt 
    ( 
        (v1.X - v2.X) * (v1.X - v2.X) + 
        (v1.Y - v2.Y) * (v1.Y - v2.Y) + 
        (v1.Z - v2.Z) * (v1.Z - v2.Z) 
    ), 5);

http://msdn.microsoft.com/en-us/library/aa340228.aspx

Answer 2

Math.Round(val, 5);

Answer 3

There's no floating point encoding for exactly N decimal digits of precision. Use decimal if you want that.

If you only want 7 digits precision stored then return a float, which conveniently has just that.

public static float Distance(Vector3 v1, Vector3 v2)
{        
    return
    (
        (float)Math.Sqrt
        (
            (v1.X - v2.X) * (v1.X - v2.X) +
            (v1.Y - v2.Y) * (v1.Y - v2.Y) +
            (v1.Z - v2.Z) * (v1.Z - v2.Z)
        )
    );
}

If you want to display 7 digits of precision then: result.ToString("F7");

Answer 4

This is a very wrong-headed approach. You never want to intentionally throw accuracy away in your program. Your computer is patient, it has no trouble keeping track of up to 15 significant digits in a number. Which is as much as you'll ever get out a double value. You'll get in deep trouble if you intentionally make it less accurate and keep using the resulting values in further computations.

Only people care what the number looks like. Accommodate that by displaying the value to human eyes and then get rid of noise digits. Like:

Console.WriteLine("{0:N5}", value);

or

string output = value.ToString("N5");