User-Defined Conversions:A Simple Example
/*
A Programmer's Introduction to C# (Second Edition)
by Eric Gunnerson
Publisher: Apress L.P.
ISBN: 1-893115-62-3
*/
// 24 - User-Defined Conversions\A 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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