我可以在 for 循环的初始化中声明不同类型的变量吗?
问题描述：
为什么这段 C++ 代码在 VS2010 下无法编译:
Why does this C++ code not compile under VS2010:
for ( int a = 0, short b = 0; a < 10; ++a, ++b ) {}
虽然这个是:
short b = 0;
for ( int a = 0; a < 10; ++a, ++b ) {}
是否禁止在for循环初始化器中声明两个不同类型的变量?如果是这样，您如何解决它?
Is the declaration of two variables of different types inside the for-loop initializer prohibited? If so, how can you work around it?
答
是的，这是被禁止的.就像否则你不能在一个声明语句中声明不同类型的变量一样(编辑:以@MrLister 提到的声明符修饰符为模).您可以声明结构
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
for (struct { int a = 0; short b = 0; } d; d.a < 10; ++d.a, ++d.b ) {}
C++03 代码:
for (struct { int a; short b; } d = { 0, 0 }; d.a < 10; ++d.a, ++d.b ) {}
当然，当全部为0时，您可以完全省略初始化器并编写= { }.
Of course when all are 0, you can omit the initializers altogether and write = { }.