c++ - 用许多算术运算符计算许多值 c++

Question

1. #ifndef CALC_H
   #define CALC_H
   
   
   class calc
   {
       double numb1;
       double numb2;
       public:
           calc();
           void FUN_SUM();
           void FUN_Subtraction();
           void FUN_Multiplication();
           void FUN_Division();
           void FUN_Power();
           void FUN_Squareroot();
           void FUN_Switch();
           void FUN_Loob();
   
   };
   
   #endif // CALC_H
   
   
   
   #include "calc.h"
   #include <iostream>
   #include <cmath>
   using namespace std;
   calc::calc()
   {
       numb1 = 0;
       numb2 = 0;
   }
   void calc::FUN_SUM()
   {
        cout << "Enter number 1 " << endl;
       cin >> numb1;
       cout << "Enter number 2 " << endl;
       cin >> numb2;
       double Result_Of_Sum;
       Result_Of_Sum = numb1+numb2;
       cout << "The result of Sum = " << Result_Of_Sum << endl;
   
   
   }
   
   void calc::FUN_Subtraction()
   {
        cout << "Enter number 1 " << endl;
    cin >> numb1;
    cout << "Enter number 2 " << endl;
    cin >> numb2;
    double Result_Of_Subtraction;
    Result_Of_Subtraction = numb1 - numb2;
    cout << "The result of Subtraction = " << Result_Of_Subtraction << endl;
   }
   void calc::FUN_Multiplication()
   {
        cout << "Enter number 1 " << endl;
       cin >> numb1;
       cout << "Enter number 2 " << endl;
       cin >> numb2;
       double Result_Of_Multiplication;
       Result_Of_Multiplication = numb1*numb2;
       cout << "The result of Multiplication = " << Result_Of_Multiplication << endl;
   
   }
   
   void calc::FUN_Division()
   {
       cout << "Enter number 1 " << endl;
       cin >> numb1;
       cout << "Enter number 2 " << endl;
       cin >> numb2;
       double Result_Of_Division ;
       Result_Of_Division = numb1/numb2;
       cout << "The result of Division = " << Result_Of_Division << endl;
   }
   
   void calc::FUN_Power()
   {
       cout << "Enter number 1 " << endl;
   cin >> numb1;
   cout << "Enter number 2 " << endl;
   cin >> numb2;
   double Result_Of_Power;
   Result_Of_Power = pow(numb1,numb2);
   cout << "The result of Power = " << Result_Of_Power << endl;
   }
   
   void calc::FUN_Squareroot()
   {
       cout << "Enter the tow number you want Square root \n";
       cin >> numb1;
   
       double Result_Of_Square_root;
       Result_Of_Square_root = sqrt(numb1);
       cout << "The result of Square root = " << Result_Of_Square_root << endl;
   }
   void calc::FUN_Switch()
   {
    int S;
       cout << "Enter the number you operator do you want do it  " << endl;
       cout << "1- Addition" << endl;
       cout << "2- Subtraction" << endl;
       cout << "3- Multiplication" << endl;
       cout << "4- Division" << endl;
       cout << "5- Power" << endl;
        cout << "6- Square Root" << endl;
         cout << "7- Exit" << endl;
       cin >> S;
   
       switch (S)
       {
       case 1:
   
           FUN_SUM();
           break;
   
       case 2:
   
           FUN_Subtraction();
           break;
   
       case 3:
   
           FUN_Multiplication();
           break;
   
       case 4:
   
           FUN_Division();
           break;
   
       case 5:
   
           FUN_Power();
           break;
   
       case 6:
   
           FUN_Squareroot();
           break;
   
       default :
           break;
   
       }
   }
   
   void calc::FUN_Loob()
   {
        char L;
   
       do
       {
   
           FUN_Switch();
   
    cout << "Do you want do another operator ( 'y' or 'n'?) \n";
           cin >> L;
   if (L== 'y' || L=='Y' || L=='n' || L=='N')
   
       continue;
   else
       cout << "you are enter roang later\n";
   
       }
   
       while (L == 'Y' || L == 'y' );
   
   }
   
   
   #include <iostream>
   #include "calc.h"
   using namespace std;
   
   int main()
   {
     cout << "Welcome to my simple Calculator\n";
   calc simple_calc;
   
   simple_calc.FUN_Loob();
   cout << "\n Tank you for use my App :) :) " << endl;
   
   return 0; 
   }
   

我的问题是如何使用常规计算器等运算符启用用户计算任何值

例如 1+9*8-1+5 我希望我的程序这样做，但我不知道怎么做？？:( :(

Answer 1

编写计算器并不是一件容易的事，因为涉及的内容更多：

1. 运算符优先级
2. 分组
3. 表达式的评估

运算符优先级
运算符优先级是操作的分组，例如在加减之前执行所有乘法和除法。计算器程序应该处理不带括号的优先级（分组）。

分组
更高级的计算器将允许使用括号对表达式进行分组。计算器应该能够评估最内部的表达式并向外工作。

表达式求值
这意味着允许多于 1 位的数字，以及数字和符号之间的空格。此外，一旦解析了表达式，就需要对其进行评估。计算器应根据操作（由用户指定）调用相应的函数。

我建议您允许用户输入表达式，然后您的程序将其作为字符串读入。然后，您的程序将解析字符串，然后评估表达式。

在网络和 StackOverflow 中搜索“c++ 计算器”以获取示例。