运算符重载的部分代码

visual basic 2005 技术内部中第六章第七节运算符重载代码。 operator部分： Module Module1 Sub Main() End Sub End Module Public Structure Fraction 'Read-Only fields Private num As Long Private den As Long 'Read-Only properties Public ReadOnly Property Numerator() As Long Get Return num End Get End Property Public ReadOnly Property Denominator() As Long Get Return den End Get End Property Sub New(ByVal numerator As Long, ByVal denominator As Long) 'Normalize the numerator and denominator If numerator = 0 Then numerator = 1 ElseIf denominator < 0 Then numerator = -numerator denominator = -denominator End If Dim div As Long = GCD(numerator, denominator) num = numerator \ div den = denominator \ div End Sub 'the greatest common divisor of two numbers (helper method) Private Function GCD(ByVal n1 As Long, ByVal n2 As Long) As Long n1 = Math.Abs(n1) n2 = Math.Abs(n2) Do 'ensure that n1>n2 If n1 < n2 Then Dim tmp As Long = n1 n1 = n2 n2 = tmp End If n1 = n1 Mod n2 Loop While n1 <> 0 End Function 'override ToString to provide a textual representation of the fraction Public Overrides Function ToString() As String If num = 0 OrElse den = 1 Then Return num.ToString Else Return String.Format("{0}/{1}", num, den) End If End Function Public Shared Operator +(ByVal f1 As Fraction, ByVal f2 As Fraction) As Fraction 'a/b+c/d=(a*d+b*c)/(b*d) Return New Fraction(f1.num * f2.den + f2.num * f1.den, f1.den * f2.den) End Operator Public Shared Operator -(ByVal f1 As Fraction, ByVal f2 As Fraction) 'a/b-c/d=(a*d-b*c)/(b*d) Return New Fraction(f1.num * f2.num, f1.den * f2.den) End Operator Public Shared Operator *(ByVal f1 As Fraction, ByVal f2 As Fraction) 'a/b * c/d=(a*c)/(b*d) Return New Fraction(f1.num * f2.num, f1.den * f2.den) End Operator Public Shared Operator /(ByVal f1 As Fraction, ByVal f2 As Fraction) Return New Fraction(f1.num * f2.den, f1.den * f2.num) End Operator End Structure