It could be done using Recursive Lambda Expression, for example,
class Program
{
static Func<int, int> Factorial = x => x < 0 ? -1 : x == 1 || x == 0 ? 1 : x * Factorial(x - 1);
static void Main(string[] args)
{
Console.WriteLine(Factorial(5));
}
}
(The code is based on the References sites.)
From the above code,
Factorial is variable of type
Func<int,int> which is holding a anonymous method. So following line of code...
x => x < 0 ? -1 : x == 1 || x == 0 ? 1 : x * Factorial(x - 1)
...is the anonymous method and is equivalent to:
int Factorial( int x ){
if( x<0){
return -1;
}else if( x==1 || x==0 )
{
return 1;
}else{
return x* Factorial(x-1);
}
}
It is also possible to generate a Factorial for a number without recursion, for example, the following code block will calculate without the recursive method call:
private static int Factorial(int i)
{
int result = i < 0 ? -1 : i == 0 || i == 1 ? 1 : 1;
if (i > 0)
Enumerable.Range(1, i).ToList<int>().ForEach(element => result = result * element);
return result;
}
and also using
Aggregate function of Linq:
private static int Factorial(int i)
{
return i < 0 ? -1 : i == 0 || i == 1 ? 1 : Enumerable.Range(1, i).Aggregate((counter, value) => counter * value);
}
(initial idea to use Aggregate function found in here[^].)
References
[1]
http://msdn.microsoft.com/en-us/library/0yw3tz5k(VS.80).aspx[
^]
[2]
http://en.wikipedia.org/wiki/Recursion[
^]
[3]
Factorial Simplified using lambda[
^]
[4]
http://stackoverflow.com/questions/1426715/factorial-of-n-numbers-using-c-lambda[
^]
[5]
http://blogs.msdn.com/b/madst/archive/2007/05/11/recursive-lambda-expressions.aspx[
^]
:)
