一個簡單的加法，減法，乘法和除法程序

Question

一個簡單的C++的計算器程序來計算加法，減法，乘法和加法...

#include <iostream> 
#include <string> 
using namespace std; 

int main() 
{ 
    //input declarations as doubles for total and counter 
    double total = 0, counter =0; 
    //input declarations sign and Q as character 
    char sign, Q = 0; 
    //input declaration value as double 
    double value; 



     //A do..while will loop forever (or until we hit the break statement) 
     do 
     { 
      //The current value is 0. 
      cout << "Result :"<<" "<< total << '\n'; 

      //Please enter an operation 
      cout << "Please enter an operation and number : "; 
     cin >> sign; 

     //If the operation is Q, the program will end. 
     if (sign != 'Q') 

     cin >> value; 
      cin.ignore(); 


      // If the value input is <=0, you can't divide anything by zero. 
      if (value <= 0) 
      { 
       cout << "Unknown Operator " << sign <<'\n' ; 
      } 

      //Otherwise procede with the calulator program 
      else 
      { 
       //If the operation is equal to '+', then the total is added. 
       if (sign == '+') 
       { 
        total += value; 
       } 

       // If the operation is equal to '-', then the value is subtracted from the previous number input. 
       else 
       { 
        if (sign == '-') 
        { 
         total -= value; 
        } 

        // If the operation is equal to '*', then the value is multiplied to the previous number input. 
        else 
        { 
         if (sign == '*') 
         { 
          total *= value; 
         } 

         // If the operation is equal to '/', then the value is divided by the previous number input. 
         else 
         { 
          if ((sign == '/')&&(value != 0)) 
          { 
           total /= value; 
          } 
         } 
        } 
       } 
      } 
     } 



      //While the operation is not equal to 'Q', the program will run. 
      while (sign != 'Q'); 



     return 0; 
} 

用於上述程序的編碼沒有錯誤，但如果我按「Q」退出，它將顯示最後的結果不間斷。 。一遍又一遍。 。 。無論如何，任何人都知道如何爲程序添加平方根。 。

Answer 1

作爲一個簡單的練習，我重構了您的程序，使其更簡單。我不能保證它的工作原理，但它應該給你一個很好的基礎，建立在：

#include <iostream> 
#include <string> 
using namespace std; 

int main() 
{ 
    //input declarations as doubles for total and counter 
    double total = 0, counter =0; 
    //input declarations sign and Q as character 
    char sign = 0; 
    //input declaration value as double 
    double value; 

    //A do..while will loop forever (or until we hit the break statement) 
    do 
    { 
    //The current value is 0. 
    cout << "Current result: " << total << '\n'; 

    //Please enter an operation 
    cout << "Please enter an operation (or Q to quit) and number: "; 
    cin >> sign; 

    //If the operation is Q, the program will end. 
    if (sign == 'Q' || sign == 'q') { 
     cout << "See you!\n"; 
     break; 
    } 

    // If the input cannot be transformed into a double 
    // abort loop and try again 
    if (!(cin >> value)) { 
     cerr << "Invalid value entered, try again\n"; 
     continue; 
    } 

    switch(sign) 
    { 
    case '+': total += value; break; 
    case '-': total -= value; break; 
    case '*': total *= value; break; 
    case '/': 
     if (value == 0) { 
     cerr << "Divide by 0 prevented!\n"; 
     } else { 
     total /= value; break; 
     } 
    default: 
     cerr << "Unknown sign: " << sign << "\n"; 
    } 

    } while (true); 

    return 0; 
} 

要點：

• 避免壓痕可能時，他們妨礙可讀性（更喜歡繼續/中斷）
• 使用開關時，可能（也可能爲char和數字）
• 檢查錯誤在必要的時候：從用戶輸入到double轉換可能會失敗，0可能是耳鼻喉科ered

Answer 2

#include <math.h> 
double result = sqrt (value); 

Answer 3

通過if (sign == 'Q') break;

• 此更換if (sign != 'Q') ...將解決衆多可能出現的錯誤。
• 這將使您的代碼更易於使用較少的縮進和大括號。

編輯：正如有人提到，你應該也可以檢查小寫字母。 （if（sign =='Q'|| sign =='q'））。

Answer 4

對於平方根， #include <math> double r=sqrt(e);

關於你的其他問題：請縮進代碼更好;-)

你確定你沒有忘記把塊這一行之後？ if (sign != 'Q')

最簡單的方法，在步進模式下使用調試器，你就會明白！