Question

前几天我正在使用xcode，正在开发基于文本的对话游戏。

#include <iostream>

int main()
{
    std::cout<<"Conversation simulator requires you to type in all caps for all  of your replies"<<std::endl;
    std::cout<<"Type your first and last name!"<<std::endl;
    std::string fname = " ";
    std::string lname = " ";
    bool samename = false;
    std::cin>> fname >> lname ;
    if  (fname == "MUSCLE" and lname == "MAN")
        std::cout<< "Wow, we have the same first and last name!"<<std::endl;
        samename = true;
    else
        std::cout<< fname << " "<< lname << "is a very nice name"<<std::endl;

return 0;
}

对我来说似乎没有什么不对，但Xcode不会因为在这条线上而无法运行：

else

它期待一个表达？我无法想到这可能意味着什么。

Answer 1

如果您希望在if下执行多个语句，则需要大括号。这是一个为我编译的修复程序。

#include <iostream>

int main()
{
        std::cout<<"Conversation simulator requires you to type in all caps for all  of your replies"<<std::endl;
        std::cout<<"Type your first and last name!"<<std::endl;
        std::string fname = " ";
        std::string lname = " ";
        bool samename = false;
        std::cin>> fname >> lname;
        if  (fname == "MUSCLE" and lname == "MAN") {
                std::cout<< "Wow, we have the same first and last name!"<<std::endl;
                samename = true;
        } else {
                std::cout<< fname << " "<< lname << "is a very nice name"<<std::endl;
        }
        return 0;
}

Answer 2

你忘记了if-block的花括号：

if  (fname == "MUSCLE" and lname == "MAN") {
    std::cout<< "Wow, we have the same first and last name!"<<std::endl;
    samename = true;
}
else
    std::cout<< fname << " "<< lname << "is a very nice name"<<std::endl;

没有它们，只有下一个语句（在你的情况下输出）属于if。因此，在下一行中设置标记会导致else不正确。

Answer 3

您忘记了以下if .. else语句中的括号是修复。

#include <iostream>

int main()
{
    std::cout<<"Conversation simulator requires you to type in all caps for all  of your replies"<<std::endl;
    std::cout<<"Type your first and last name!"<<std::endl;
    std::string fname = " ";
    std::string lname = " ";
    bool samename = false;
    std::cin>> fname >> lname ;
    if  (fname == "MUSCLE" and lname == "MAN"){
        std::cout<< "Wow, we have the same first and last name!"<<std::endl;
        samename = true;
    } else {
        std::cout<< fname << " "<< lname << "is a very nice name"<<std::endl;
    }
return 0;
}

Answer 4

你错过了括号：

If () {
} else {
}

Answer 5

我相信必须使用Open-Close花括号：

if  (fname == "MUSCLE" and lname == "MAN")
{
    std::cout<< "Wow, we have the same first and last name!"<<std::endl;
    samename = true;
}
else
    std::cout<< fname << " "<< lname << "is a very nice name"<<std::endl;

C ++ if / else语句问题

5 个答案: