C++ 错误：'cout'：未声明的标识符；虽然我已经在程序中包含了 iostream 头文件
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Error: 'cout' : undeclared identifier; though I've included iostream header file in program
提问by yuvi
I am trying to compile the simple program below. But, it's not compiling & gives error:
我正在尝试编译下面的简单程序。但是，它没有编译并给出错误：
error C2065: 'cout' : undeclared identifier
I want to ask you that why this program doesn't work though I've included iostreamheader file in it?
我想问你，为什么这个程序虽然我已经包含了iostream头文件，但它不起作用？
#include <iostream>
void function(int) { cout << “function(int) called” << endl; }
void function(unsigned int) { cout << “function(unsigned int) called” << endl; }
int main()
{
function(-2);
function(4);
return 0;
}
Thanks in advance.
提前致谢。
回答by David Heffernan
The cout stream is defined in the std namespace. So to name it you write:
cout 流在 std 命名空间中定义。所以命名它你写：
std::cout
If you want to shorten this to cout then you can write
如果你想缩短这个 cout 那么你可以写
using namespace std;
or
或者
using std::cout;
before writing cout.
在写 cout 之前。
Any good documentation source will tell you which namespace contains an object. For instance: http://en.cppreference.com/w/cpp/io/cout
任何好的文档源都会告诉您哪个命名空间包含一个对象。例如：http: //en.cppreference.com/w/cpp/io/cout
回答by Uri Y
You have to write std::coutor add using std;
你必须写std::cout或添加using std;
