ç簡單的計算器錯誤

Question

我想使它所以如果一個字符輸入在開始，而不是1,2,3或4那麼它將循環回輪，除了說

cout << "You have entered a incorrect operator" << endl; 

我已經嘗試了包括default:的情況，但似乎並沒有影響它的數量。

任何人都可以擺脫任何光線？

http://pastebin.com/9U7sEEzL

#include <iostream> 
#include <string> 

void start() 
{ 
    using namespace std; 

    cout << "Welcome to my Basic Mini-Calculator!" << endl; 
} 

int choice() 
{ 
    using namespace std; 

    int uChoice; 

    cout << endl << "What do you want to do?" << endl; 
    cout << "1) Add" << endl; 
    cout << "2) Subtract" << endl; 
    cout << "3) Multiply" << endl; 
    cout << "4) Divide" << endl; 
    cout << endl << "Waiting for input... (enter a number): "; 
    cin >> uChoice; 
    cout << endl; 

    while(uChoice != 1 && uChoice != 2 && uChoice != 3 && uChoice != 4); 

    switch (uChoice) 
    { 
     case 1: 
      cout << endl << "You chose addition." << endl; 
      break; 

     case 2: 
      cout << endl << "You chose subtraction." << endl; 
      break; 

     case 3: 
      cout << endl << "You chose multiplication." << endl; 
      break; 

     case 4: 
      cout << endl << "You chose division." << endl; 
      break; 
    } 

    return uChoice; 



} 

int input(bool i = false) 
{ 
    using namespace std; 

    string text; 

    text = (i == true) ? "Enter another number: " : "Enter a number: "; 
    cout << endl << text; 

    float number; 
    cin >> number; 

    return number; 
} 

int work(int one, int two, int todo) 
{ 
    using namespace std; 

    float answer; 

    switch (todo) 
    { 
     case 1: 
      answer = one + two; 
      break; 

     case 2: 
      answer = one - two; 
      break; 

     case 3: 
      answer = one * two; 
      break; 

     case 4: 
      answer = one/two; 
      break; 

     default: cout << "Please choose a proper number (1-4)" << endl; 
    } 


    return answer; 
} 

void answer(int theanswer) 
{ 
    using namespace std; 

    cout << endl << "The answer is " << theanswer << "." << endl; 
    cout << endl << "Hit Return to exit."; 

    cin.clear(); 
    cin.ignore(255, '\n'); 
    cin.get(); 
} 

int main() 
{ 
    using namespace std; 

    start(); 

    int todo = choice(); 

    float one = input(); 
    float two = input(true); 

    float theanswer = work(one, two, todo); 


    answer(theanswer); 

    return 0; 
} 

Answer 1

只需添加一個do：

do 
{ 
cout << endl << "What do you want to do?" << endl; 
cout << "1) Add" << endl; 
cout << "2) Subtract" << endl; 
cout << "3) Multiply" << endl; 
cout << "4) Divide" << endl; 
cout << endl << "Waiting for input... (enter a number): "; 
cin >> uChoice; 
cout << endl; 

} while(uChoice != 1 && uChoice != 2 && uChoice != 3 && uChoice != 4); 

Answer 2

當您嘗試讀取了號碼，但您會收到無效的輸入爲，流進入一個「失敗國家」。您可以檢查這個「cin.fail（）」，或者你使用整個流作爲參數：

// try reading 
while(!(cin >> n)) 
{ 
    cin.clear(); // reset fail state 
    string s; 
    getline(cin, s); // discard remaining line 
} 

這就是說，請降低你的代碼下一次小例子。