C++ 错误：“<<”标记之前的预期主表达式

Question

I have written a very simple C++ code but I don't know why I am getting this error. Can anyone help me?

#include <iostream>
using namespace std;

#define MKSTR( x ) #x
#define concat(a,b) a ## b;
int main () {
    int xy = 100;
    cout << MKSTR(HELLO C++) << endl;
    cout << concat(x,y) << endl;  // I am getting an error here
   return 0;
}

Answer 1

#define concat(a,b) a ## b;
                          ^

Extraneous semi-colon.

Answer 2

define is a pre-processor directive and doesn't require a semi-colon, remove it.

#define concat(a,b) a ## b