C++ cin 未在此范围内使用 g++ 错误声明
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cin not declared in this scope error with g++
提问by qed
Here is the code:
这是代码：
#include <stdlib.h>
#include <iostream>
int main() {
std::cout << "Enter two numbers: " << std::endl;
int v1 = 0, v2 = 0;
std:cin >> v1 >> v2;
std::cout << "The sum of " << v1 << "and " v2 << "is " << v1+v2 << std:endl;
return 0;
}
Here is the error:
这是错误：
g++ x.cpp
#x.cpp: In function ‘int main()':
#x.cpp:23:9: error: ‘cin' was not declared in this scope
#x.cpp:23:9: note: suggested alternative:
#In file included from x.cpp:19:0:
#/usr/include/c++/4.7/iostream:61:18: note: ‘std::cin'
#x.cpp:24:48: error: expected ‘;' before ‘v2'
I have corrected the code, there are several mistakes (this is my first c++ experience):
我已经更正了代码，有几个错误（这是我的第一次c++体验）：
#include <stdlib.h>
#include <iostream>
int main() {
std::cout << "Enter two numbers: " << std::endl;
int v1 = 0, v2 = 0;
std::cin >> v1 >> v2;
std::cout << "The sum of " << v1 << " and " << v2 << " is " << v1+v2 << std::endl;
return 0;
}
回答by Andy Prowl
Here:
这里：
std:cin >> v1 >> v2;
// ^
You are missing a colon. It should be:
你少了一个冒号。它应该是：
std::cin >> v1 >> v2;
// ^^
Without the second colon, instead of using the scope resolution operator, you are declaring a labelcalled std, followed by an unqualified name cin(which is why the compiler complains about cinnot being declared in this scope).
没有第二个冒号，而不是使用范围解析运算符，您将声明一个名为的标签std，后跟一个非限定名称cin（这就是编译器抱怨cin未在此范围内声明的原因）。
