如何删除OR'd枚举的项目？ [英] How to remove an item for a OR'd enum?

问题描述

我有一个枚举：

  public enum Blah 
 {
 RED = 2，
 BLUE = 4，
 GREEN = 8，
 YELLOW = 16 
} 
 
 Blah colors = Blah.RED | Blah.BLUE | Blah.YELLOW; 
  

如何从变量颜色中删除蓝色？

<您需要使用〜

补码运算符基本上反转或翻转给定数据类型的所有位。因此，如果您使用具有某些值的 AND 运算符（& ）（让我们称该值为'X' ）和一个或多个设置位的补码（我们称之为 Q 及其补码〜Q ），声明 X& 〜Q 清除在 Q 中从 X 中设置的任何位，并返回结果。

为了删除或清除 BLUE 位，您使用以下语句：

  colorsWithoutBlue = colors& 〜Blah.BLUE 
 colors& =〜Blah.BLUE //这个从颜色本身中删除位
  

您还可以指定要清除的多个位，如下所示：

  colorsWithoutBlueOrRed = colors& 〜（Blah.BLUE | Blah.RED）
 colors& =〜（Blah.BLUE | Blah.RED）//这个从颜色本身去除两个位元
  

或者交替地...

  colorsWithoutBlueOrRed =颜色& 〜Blah.BLUE& 〜Blah.RED 
 colors& =〜Blah.BLUE& 〜Blah.RED //这个从颜色本身删除了两个位
  

所以总结一下： / p>

• X | Q 设置位 Q


• X& 〜Q 清除位 Q


• 〜X 翻转/翻转 X中的所有位

I have an enum like:

public enum Blah
{
    RED = 2,
    BLUE = 4,
    GREEN = 8,
    YELLOW = 16
}

Blah colors = Blah.RED | Blah.BLUE | Blah.YELLOW;

How could I remove the color blue from the variable colors?

解决方案

You need to & it with the ~ (complement) of 'BLUE'.

The complement operator essentially reverses or 'flips' all bits for the given data type. As such, if you use the AND operator (&) with some value (let's call that value 'X') and the complement of one or more set bits (let's call those bits Q and their complement ~Q), the statement X & ~Q clears any bits that were set in Q from X and returns the result.

So to remove or clear the BLUE bits, you use the following statement:

colorsWithoutBlue = colors & ~Blah.BLUE
colors &= ~Blah.BLUE // This one removes the bit from 'colors' itself

You can also specify multiple bits to clear, as follows:

colorsWithoutBlueOrRed = colors & ~(Blah.BLUE | Blah.RED)
colors &= ~(Blah.BLUE | Blah.RED) // This one removes both bits from 'colors' itself

or alternately...

colorsWithoutBlueOrRed = colors & ~Blah.BLUE & ~Blah.RED
colors &= ~Blah.BLUE & ~Blah.RED // This one removes both bits from 'colors' itself

So to summarize:

• X | Q sets bit(s) Q
• X & ~Q clears bit(s) Q
• ~X flips/inverts all bits in X

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