User-Defined Conversions:A Simple Example

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/*
A Programmer's Introduction to C# (Second Edition)
by Eric Gunnerson

Publisher: Apress  L.P.
ISBN: 1-893115-62-3
*/
// 24 - User-Defined ConversionsA Simple Example
// copyright 2000 Eric Gunnerson
using System;
using System.Text;
struct RomanNumeral
{
    public RomanNumeral(short value) {
        if (value > 5000)
        throw(new ArgumentOutOfRangeException());
        
        this.value = value;
    }
    public static explicit operator RomanNumeral(short value) 
    {
        RomanNumeral    retval;
        retval = new RomanNumeral(value);
        return(retval);
    }
    
    public static implicit operator short(RomanNumeral roman)
    {
        return(roman.value);
    }
    
    static string NumberString(ref int value, int magnitude, char letter)
    {
        StringBuilder    numberString = new StringBuilder();
        
        while (value >= magnitude)
        {
            value -= magnitude;
            numberString.Append(letter);
        }
        return(numberString.ToString());
    }
    
    public static implicit operator string(
    RomanNumeral roman)
    {
        int        temp = roman.value;
        
        StringBuilder retval = new StringBuilder();
        
        retval.Append(RomanNumeral.NumberString(ref temp, 1000, 'M'));
        retval.Append(RomanNumeral.NumberString(ref temp, 500, 'D'));
        retval.Append(RomanNumeral.NumberString(ref temp, 100, 'C'));
        retval.Append(RomanNumeral.NumberString(ref temp, 50, 'L'));
        retval.Append(RomanNumeral.NumberString(ref temp, 10, 'X'));
        retval.Append(RomanNumeral.NumberString(ref temp, 5, 'V'));
        retval.Append(RomanNumeral.NumberString(ref temp, 1, 'I'));
        
        return(retval.ToString());
    }
    
    private short value;
}

public class UserDefinedConversionsASimpleExample
{
    public static void Main()
    {
        short s = 12;
        RomanNumeral numeral = new RomanNumeral(s);
        
        s = 165;
        numeral = (RomanNumeral) s;
        
        Console.WriteLine("Roman as int: {0}", (int)numeral);
        Console.WriteLine("Roman as string: {0}", (string)numeral);
        
        short s2 = numeral;
    }
}

           
         
    
     


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