if語句正在運行時只有一條語句

-1

我在C++中提出了一個程序，要求輸入任何整數。該程序只有2次迭代後崩潰。代碼如下：if語句正在運行時只有一條語句

#include<iostream> 

int main() 
{ 
    int user_choice; 
    std::cout <<"Please enter any number other than five: "; 
    std::cin >> user_choice; 

    while(user_choice != 5) 
    { 
     std::cout <<"Please enter any number other than five: "; 
     std::cin >> user_choice; 
     if(user_choice == 5) 
      std::cout << "Program Crash"; 
      break; 
    } 
    std::cout << "I told you not to enter 5!"; 
    return 0; 
}

然後我試着這樣做：

if(user_choice == 5) 
    std::cout << "Program Crash"; 
    //std::cout << "Shutting Down";

哪些工作。爲什麼註釋掉第二行，導致程序運行正常？

來源

2016-07-31 Christian Dean

'if（condition）{statement1;語句2; }' – LogicStuff

@LogicStuff能否請你解釋一下你的評論 –

還有更多的代碼，比如，你爲什麼要比較'user_choice'和'5'文字，你應該做'user_choice == right_answer'？爲什麼你覺得有必要將'right_answer'分配給'user_choice'如果它們已經相等了？你還將'5'硬編碼到輸出消息中...... – LogicStuff

此代碼：

if (counter == 10) 
    std::cout << "Wow you still have not entered 5. You win!"; 
    user_choice = right_answer;

Is eq uivalent到：

if (counter == 10) 
{ 
    std::cout << "Wow you still have not entered 5. You win!"; 
} 
user_choice = right_answer;

你的問題變得明顯，user_choice = right_answer不執行，只有當counter == 10。因此，將其移動到if() { ... }塊內：

if (counter == 10) 
{ 
    std::cout << "Wow you still have not entered 5. You win!"; 
    user_choice = right_answer; 
}

來源

2016-07-31 21:10:25 user2296177

@ Mr.Python絕對不會，如果你還沒有，可以拿一本C++書。你不能跳入C++並應用其他語言的結構......你會遇到類似的問題。 – user2296177

@ Mr.Python我建議在那裏查找「範圍」。 – user2296177

是的，實際上學習語言讓你更擅長這一點令人驚訝。 –

C++不尊重縮進;所以，當你寫：

if (counter == 10) 
    std::cout << "Wow you still have not entered 5. You win!"; 
    user_choice = right_answer;

編譯器看到：

if (counter == 10) 
    std::cout << "Wow you still have not entered 5. You win!"; 
user_choice = right_answer;

爲了把兩個語句下if，你需要括號：

if (counter == 10) { 
    std::cout << "Wow you still have not entered 5. You win!"; 
    user_choice = right_answer; 
}

來源

2016-07-31 21:10:22

if語句正在運行時只有一條語句

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