我可以在 for 循环的初始化中声明不同类型的变量吗？
为什么这个 C++ 代码在 VS2010 下无法编译：
for ( int a = 0, short b = 0; a < 10; ++a, ++b ) {}
而这个却可以：
short b = 0;
for ( int a = 0; a < 10; ++a, ++b ) {}
for 循环初始化器中禁止声明两个不同类型的变量吗？如果是这样，你该如何解决这个问题？
Why does this C++ code not compile under VS2010:
for ( int a = 0, short b = 0; a < 10; ++a, ++b ) {}
while this one does:
short b = 0;
for ( int a = 0; a < 10; ++a, ++b ) {}
Is the declaration of two variables of different types inside the for-loop initializer prohibited? If so, how can you work around it?
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评论（5）
是的，这是禁止的。正如其他情况一样，您不能在一个声明语句中声明不同类型的变量（编辑：以 @MrLister 提到的声明符修饰符为模）。您可以声明结构体
C++03 代码：
当然，当全部为
0时，您可以完全省略初始值设定项并编写= { }。Yes, that is prohibited. Just as otherwise you cannot declare variables of differing types in one declaration statement (edit: modulo the declarator modifiers that @MrLister mentions). You can declare structs
C++03 code:
Of course when all are
0, you can omit the initializers altogether and write= { }.与 for 循环无关。如果您在任何循环之外编写
int a = 0, Short b = 0;，这也不会编译。所以答案是：总是禁止在一条语句中声明两个不同类型的变量。
编辑：哦，对于迂腐的人来说，我确实意识到您可以在同一语句中声明基类型和指针类型，例如 int 和 int 指针，所以它们将是不同的类型，是的。
嗯，这让我思考。在 32 位环境中，指针将是 4 个字节，就像 int 一样，因此您可以使用短 a = 0, *b = 0;然后将 b 转换为 int。嗯...
Nothing to do with the
forloop. This also doesn't compile if you writeint a = 0, short b = 0;outside of any loop.So the answer is: it is always forbidden to declare two variables of different types in a single statement.
Edit: Oh, for the pedantic, I do realise that you can declare a base type and a pointer type in the same statement, for instance an int and an int pointer, so those would be different types, yes.
Hm, that makes me think. In a 32 bit environment, a pointer would be 4 bytes, just like an int, so you could use short a = 0, *b = 0; and then cast b to an int. Hm...
禁止的是以逗号结尾的语句，就像 int a = 0, short ...
如果您想使用此表示法，则变量 muss 具有相同的类型
int i = 0, s = 0;What is prohibited is the ending of a statement with a comma as you do in
int a = 0, short ...If you want to use this notation then bothe variable muss have the same type
int i = 0, s = 0;for 语句中只能声明一种类型。所以第二个代码是可用的。
You can only declare one type in for statement. So the second code is the usable one.
您不能在
for（comprobation 步骤）的while条件中声明变量。那都行不通。
You can't declare a variable into the
whilecondition of thefor(the comprobation step).that's neither works.