Math.Ceiling giving "Call is ambiguous" error when using String.Length

Question

Good day all.

I am getting back into C# after a few years, and am little stuck on an error I'm receiving. I wrote a practice program to determine whether a word is a palindrome (same backwards and forwards). I am however getting an error that confuses me.

I try to call Math.Ceiling(word.Length / 2) to get the middle of a word, but it gives me the following error: "The call is ambiguous between the following methods or properties:'Math.Ceiling(decimal) and Math.Ceiling(double)"

Although I get that this is the compiler worrying about identifying the correct overloaded method, but am unsure how to indicate which I am using. I also don't get why should this matter?

Here is my full program:

namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            string word = "Deleveled";
            word = word.ToUpper();
            bool isPalindrome = true;
            for (var i = 0; i <= Math.Ceiling(word.Length / 2); i++)
            {
                char tmp = word[word.Length - i - 1];
                if (Char.ToUpper(word[i]) != Char.ToUpper(tmp))
                {
                    isPalindrome = false;
                    break;
                }
            }
            Console.WriteLine(isPalindrome);
            Console.ReadLine();
        }
    }
}

I would greatly appreciate it f anyone could help me understand what the issue is here?

My thanks in advance

Answer 1

Integer division always results in an integer; so: word.Length / 2 returns int (it rounds down).

When you call Math.Ceiling on this, you are passing an integer, but there is not Math.Ceiling(int). It has two choices: Math.Ceiling(double) and Math.Ceiling(decimal), but: it could use either, and neither of those is better from the compiler's perspective.

Frankly, it might be simpler to use the general purpose "page count" formula:

int pages = (items + pageSize - 1) / pageSize;

which in this case becomes simply:

int upperLimit = (word.Length + 1) / 2;

(note that the general purpose page count formula can also be written int pages = ((items - 1) / pageSize) + 1;, although in this case it would be harder to substitute your fixed page size)