utils.cs

csharp-solution,C#高效编程源码

namespace Utils
{
    using System;

    class Utils
    {

	//
	// Method to display an object, either using the Print method
	// if it implements IPrintable, or using ToString if it does not
	//

	public static void Display(object item)
	{
		IPrintable ip;

		ip = (item as IPrintable);

		if (ip != null)
			ip.Print();
		else
			Console.WriteLine(item.ToString());
	}

	//
	// Test to see whether an object supports the IFormattable interface
    // 

	public static bool IsItFormattable(object x)
	{
		// Use is to test if the object has the
		// IFormattable iterface

		if (x is IFormattable)
			return true;
		else
			return false;
	}


	//
    // Return the larger of two integer values
    //

    public static int Greater(int a, int b)
    {
        if (a>b)
            return a;
        else
            return b;

        // Alternative version - more terse
        // return (a>b) ? (a) : (b);
    }

    //
    // Swap two integers, passed by reference
    //

    public static void Swap(ref int a, ref int b)
    {
        int temp;
        temp = a;
        a = b;
        b = temp;
    }

    //
    // Calculate factorial
    // and return the result as an out parameter
    //

    public static bool Factorial(int n, out int answer)
    {
        int k;        // loop counter
        int f;        // working value
        bool ok=true; // true if ok, false if not

        // Check the input value

        if (n<0)
            ok = false;

        // Calculate the factorial value as the
        // product of all the numbers from 2 to n

        try
        {
            checked
            {
                f = 1;
                for (k=2; k<=n; ++k)
                {
                    f = f * k;
                }       

                // Here is a terse alternative
                // for (f=1,k=2;k<=n;++k)
                //     f*=k;

            }
        }
        catch(Exception)
        {
            // If something goes wrong in the calculation,
            // catch it here. All exceptions
            // are handled the same way: set the result to
            // to zero and return false.

            f = 0;
            ok = false;
        }

        // assign result value                
        answer = f;

        // return to caller
        return ok;
    }

    //
    // Another way to solve the factorial problem, this time
    // as a recursive function
    //

    public static bool RecursiveFactorial(int n, out int f)
    {
        bool ok=true;

        // Trap negative inputs
        if (n<0)
        {
                f=0;
                ok = false;
        }

        if (n<=1)
            f=1;
        else
        {
            try
            {
                int pf;
                checked
                {       
                    ok = RecursiveFactorial(n-1,out pf);
                    f = n * pf;
                }
            }
            catch(Exception)
            {
                // Something went wrong. Set error
                // flag and return zero.
                f=0;
                ok=false;
            }
                               
        }

        return ok;
    }
    }
}