允許在我的類的實例上發生數學問題

Question

是否有一些接口可以實現，以允許基本比較和數學運算，因爲它是一個整數？

例如，假設我有下面的類：

Public Class Something 
    Public SomeBigNumber as UInt64 
End Class 

我願做這樣的事情：

Dim SomethingA, SomethingB, SomethingC as New Something 

.... 

If (SomethingA-SomethingB) > SomethingC Then 
    'Do stuff 
End If 

我希望能夠實現一些接口（如即使是它的正確術語），如果可能的話，它將返回類中包含的UInt64用於比較和數學運算。

想法？提前致謝！

Answer 1

你正在尋找的是"operator overloading"，它允許你爲複雜類型（比如你的類Something）定義比較和數學運算符。

例如，你可以從你的Something類中重載加法和減法運算符是這樣的：

Public Shared Operator +(ByVal val1 As Something, ByVal val2 As Something) As Something 
    ''#(calculate the sum of the two specified values) 
    Return New Something(val1.SomeBigNumber + val2.SomeBigNumber) 
End Operator 

Public Shared Operator -(ByVal val1 As Something, ByVal val2 As Something) As Something 
    ''#(calculate the difference of the two specified values) 
    Return New Something(val1.SomeBigNumber - val2.SomeBigNumber) 
End Operator 

然後你就可以編寫代碼：

Dim newValue As Something = something1 + something2 

你也可以以幾乎完全相同的方式過載比較運算符（大於，小於，等於及其間的所有內容）：

Public Shared Operator >(ByVal val1 As Something, ByVal val2 As Something) As Boolean 
    ''#(return True if the first value is larger, False otherwise) 
    Return (val1.SomeBigNumber > val2.SomeBigNumber) 
End Operator 

Public Shared Operator <(ByVal val1 As Something, ByVal val2 As Something) As Boolean 
    ''#(return True if the first value is smaller, False otherwise) 
    Return (val1.SomeBigNumber < val2.SomeBigNumber) 
End Operator 

允許你寫的代碼，如：

If something1 > something2 Then 
    MesssageBox.Show("The first value is larger.") 
Else 
    MessageBox.Show("The second value is larger.") 
End If 

但是請注意，其中一些運營商必須在對超載。具體做法是：

• =和<>
• >和<
• >=和<=
• IsTrue和IsFalse