foreach不适用于一系列bool？ [英] foreach doesn't work with array of bools?
问题描述
将它们初始化为假。
bool [] bits = new bool [10];
foreach（bool bit in bits）
{
bit = false;
}
编译器在bit = false;上抱怨声明该位是只读的。
如果我使用索引迭代，它编译就好了：
for（int i = 0; i< ; bits.Length; i ++）
{
bits [i] = false;
}
编译得很好。发生了什么？
此外，无论如何，bool数组似乎初始化为假。我可以指望这个吗？我是否应该担心初始化它们？
谢谢。
bool [] bits = new bool [10];
foreach（bool bit in bits）
{
bit = false;
}
在此代码段中，位是指向位
数组中的一个值的指针。它是一个只读指针，所以你不能写它。
for（int i = 0; i< bits.Length; i ++）
{
bits [i] = false;
}
这使事情变得更容易处理。基本上，您直接在此代码段中设置数组成员的
值，而不是尝试通过指针访问它来获得
。因此保留了您创建的数组
的读/写性质。
HTH
Joe Rattz写道：
嗯，我写了下面的代码。我想要一系列bool，我想将它们初始化为假。
bool [] bits = new bool [10];
foreach（bool bit in bits）
{
bit = false;
}
编译器抱怨bit = false;声明该位是只读的。
如果我使用索引迭代，它编译就好了：
for（int i = 0; i< bits.Length; i ++）
{
bits [i] = false;
}
编译得很好。发生了什么？
此外，无论如何，bool阵列似乎已经初步化为假。我可以依靠吗？我是否应该担心初始化它们？
构造的bool的默认值是''false''：
http://msdn.microsoft.com/library/en。 ..nstructors.asp
另一种分配和初始化的方法是：
bool [] bits = new bool [ ] {false，false，false，false / * etc * /};
这允许您在构造中指定不同的值，例如：
bool [] bits = new bool [] {true，false，true，false / * etc * /};
Joe，
发生了什么事？
正是编译器所说的。 foreach语句中的变量是
只读。
此外，无论如何，bool数组似乎初始化为false。我可以依靠吗？
是的，你可以。创建新数组时，所有元素都具有
默认初始值。对于布尔来说，这是假的。
我是否应该担心初始化它们？
我不会浪费CPU周期。
Mattias
-
Mattias Sj？gren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
请回复到新闻组。
Hmmm, I wrote the following code. I want an array of bools and I want to
intialize them to false.
bool[] bits = new bool[10];
foreach(bool bit in bits)
{
bit = false;
}
The compiler complains on the "bit = false;" stating that bit is read-only.
If I iterate using an index though, it compiles just fine:
for(int i = 0; i < bits.Length; i++)
{
bits[i] = false;
}
That compiles just fine. What is going on?
Also, the array of bools seems to have intialized to false anyway. Can I
count on that? Should I even worry about initializing them?
Thanks.
bool[] bits = new bool[10];
foreach(bool bit in bits)
{
bit = false;
}
In this snippet, "bit" is a pointer to one of the values in the bits
array. It is a read-only pointer, though, so you cannot write to it.
for(int i = 0; i < bits.Length; i++)
{
bits[i] = false;
}
This makes things easier to deal with. Basically, you are setting the
value of an array member directly in this snippet, rather than trying
to access it through a pointer. The read/write nature of the array
you created is therefore preserved.
HTH
Joe Rattz wrote:
Hmmm, I wrote the following code. I want an array of bools and I want to
intialize them to false.
bool[] bits = new bool[10];
foreach(bool bit in bits)
{
bit = false;
}
The compiler complains on the "bit = false;" stating that bit is read-only.
If I iterate using an index though, it compiles just fine:
for(int i = 0; i < bits.Length; i++)
{
bits[i] = false;
}
That compiles just fine. What is going on?
Also, the array of bools seems to have intialized to false anyway. Can I
count on that? Should I even worry about initializing them?
The default value for a constructed bool is ''false'':
http://msdn.microsoft.com/library/en...nstructors.asp
An alternative method of alloc and initialize is:
bool[] bits = new bool[] { false, false, false, false /*etc*/ };
This allows you to specify differing values in construction, such as:
bool[] bits = new bool[] { true, false, true, false /*etc*/ };
Joe,
What is going on?
Exactly what the compiler says. The variable in a foreach statement is
read only.
Also, the array of bools seems to have intialized to false anyway. Can I
count on that?
Yes you can. When you create a new array, all elements have their
default initial value. For bool, that''s false.
Should I even worry about initializing them?
I wouldn''t waste CPU cycles on it.
Mattias
--
Mattias Sj?gren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.
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