Калькулятор с несколькими операциями

#include "stdafx.h"
#include <iostream>
 
using namespace std;
 
int main()
{
 
    float num_1, num_2, result;
    char act;
    int c = 2;
 
    cout << "1-open calc\n";
    cout << "2-close\n";
 
    cin >> c;
    switch (c)
    {
    case 1:
        while (c == 1)
        {
        ret:;
            cout << "Enter nums\n";
            cin >> num_1 >> act >> num_2;
 
 
            if (act == '+')
            {
                result = num_1 + num_2;
                cout << result << endl;
            }
            if (act == '-')
            {
                result = num_1 - num_2;
                cout << result << endl;
            }
            if (act == '*')
            {
                result = num_1 * num_2;
                cout << result << endl;
            }
            if (act == '/')
            {
                result = num_1 / num_2;
                cout << result << endl;
            }
 
            goto menu;
 
        }
    menu:;
        cout << "1-continue\n";
        cout << "2-close\n";
        cin >> c;
            if (c == 1)
            {
                goto ret;
            }
            else
            {
                break;
            }
    case 2:
        system("pause");
        return 0;
        
    }
    
    
    
}

#include <iostream>
 
class Action
{
    char m_action;
public:
    Action() : m_action('+')
    {}
 
    explicit Action(char action) : m_action(action)
    {}
 
    bool is_valid()
    {
        return
            m_action == '+' ||
            m_action == '-' ||
            m_action == '*' ||
            m_action == '/';
    }
 
    void set(char action)
    {
        m_action = action;
    }
 
    char get()
    {
        return m_action;
    }
 
    friend std::istream & operator>>(std::istream & is, Action & a)
    {
        is >> a.m_action;
        return is;
    }
};
 
int main()
{
    std::cout << "Please enter a number: ";
    double x;
    std::cin >> x;
 
    std::cout << "Please enter an action: ";
    Action action;
    std::cin >> action;
 
    while (!action.is_valid())
    {
        std::cout << "Please enter one of valid actions: +, -, * or /\n";
        std::cin >> action;
    }
 
    std::cout << "Please enter a number: ";
    double y;
    std::cin >> y;
 
    double result;
    if (action.get() == '+')
        result = x + y;
    else if (action.get() == '-')
        result = x - y;
    else if (action.get() == '*')
        result = x * y;
    else
        result = x / y;
 
    std::cout << "Result is: " << result;
}

#include <iostream>
 
bool is_valid(char action)
{
    return
        action == '+' ||
        action == '-' ||
        action == '*' ||
        action == '/';
}
 
int main()
{
    std::cout << "Please enter a number: ";
    double x;
    std::cin >> x;
 
    std::cout << "Please enter an action: ";
    char action;
    std::cin >> action;
 
    while (!is_valid(action))
    {
        std::cout << "Please enter one of valid actions: +, -, * or /\n";
        std::cin >> action;
    }
 
    std::cout << "Please enter a number: ";
    double y;
    std::cin >> y;
 
    double result;
    if (action == '+')
        result = x + y;
    else if (action == '-')
        result = x - y;
    else if (action == '*')
        result = x * y;
    else
        result = x / y;
 
    std::cout << "Result is: " << result;
}

#include <iostream>
 
bool is_valid(char action)
{
    return
        action == '+' ||
        action == '-' ||
        action == '*' ||
        action == '/';
}
 
int main()
{
    std::cout << "Hi! Welcome to ASC - Another one Simple Calculator.\n";
 
    char userChoice = 'y';
    while (userChoice == 'y')
    {
        std::cout << "\nPlease enter a number: ";
        double x;
        std::cin >> x;
 
        std::cout << "Please enter an action: ";
        char action;
        std::cin >> action;
 
        while (!is_valid(action))
        {
            std::cout << "Please enter one of valid actions: +, -, * or /\n";
            std::cin >> action;
        }
 
        std::cout << "Please enter a number: ";
        double y;
        std::cin >> y;
 
        double result;
        if (action == '+')
            result = x + y;
        else if (action == '-')
            result = x - y;
        else if (action == '*')
            result = x * y;
        else
            result = x / y;
 
        std::cout << "Result is: " << result;
 
        std::cout << "\nDo you want to proceed? (y/n): ";
        std::cin >> userChoice;
    }
}

#include <iostream>
#include <string>
#include <sstream>
 
bool is_valid(char arithmeticOperation)
{
    return
        arithmeticOperation == '+' ||
        arithmeticOperation == '-' ||
        arithmeticOperation == '*' ||
        arithmeticOperation == '/';
}
 
template<typename T> // thanks to Martin York from https://stackoverflow.com/
bool is_valid(std::string const& num)
{
    T  value;
    std::stringstream stream(num);
    stream >> value;
 
    // If the stream is already in the error state peak will not change it.
    // Otherwise stream should be good and there should be no more data
    // thus resulting in a peek returning an EOF
    return
        (stream) &&
        stream.peek() == std::char_traits<typename std::stringstream::char_type>::eof();
}
 
double get_double_from_user()
{
    std::cout << "Please enter a number: ";
    std::string numberAsString;
    std::cin >> numberAsString;
 
    while (!is_valid<double>(numberAsString))
    {
        std::cout << "Please enter valid number: ";
        std::cin >> numberAsString;
    }
 
    return std::stod(numberAsString);
}
 
char get_arithmetic_op_from_user()
{
    std::cout << "Please enter an arithmetic operation: ";
    std::string arithmeticOperation;
    std::cin >> arithmeticOperation;
 
    while (!is_valid(arithmeticOperation.at(0)))
    {
        std::cout << "Please enter one of valid arithmetic operations: +, -, * or /\n";
        std::cin >> arithmeticOperation;
    }
 
    return arithmeticOperation.at(0);
}
 
double calc_result(double x, double y, char arithmeticOperation)
{
    double result;
    if (arithmeticOperation == '+')
        result = x + y;
    else if (arithmeticOperation == '-')
        result = x - y;
    else if (arithmeticOperation == '*')
        result = x * y;
    else
        result = x / y;
 
    return result;
}
 
int main()
{
    std::cout << "Hi! Welcome to ASC - Another one Simple Calculator.\n\n";
 
    for (std::string userChoice("y"); userChoice.at(0) == 'y' || userChoice.at(0) == 'Y'; )
    {
        double x = get_double_from_user();
        char arithmeticOperation = get_arithmetic_op_from_user();
        double y = get_double_from_user();
        std::cout << "Result is: " << calc_result(x, y, arithmeticOperation);
 
        std::cout << "\nDo you want to proceed? (y/n): ";
        std::cin >> userChoice;
        std::cout << "\n";
    }
}