单行输入跟踪计算器

Question

这问题的第二部分。我已经重写了代码的大部分部分，希望这样做会更好。代码现在有一些更多的逻辑和较少的可读性。

计算器中包含的

函数：

• 添加用户输入2+2程序输出4
• 减法用户输入2-2程序输出0
• 乘法用户输入2*2程序输出4
• 除法用户输入2/2程序输出1
• 指数用户输入2^2程序输出4

#include <iostream>
#include <string>
#include <sstream>
#include <Windows.h>
#include <cmath>

class Math_Functions
{
public:
    double addition(double, double);
    double subtraction(double, double);
    double multiplication(double, double);
    void division(double, double);
    void exponentiation(double, double);
} math;

class Results_Handler
{
public:
    void division(std::string);
    void exponentiation(std::string);
} res_handler;

//This function I found somewhere in the deep internet
class Miscellaneous
{
public:
    void Pause()
    {
        std::cout << std::endl << "Press any key to continue . . . ";
        std::cin.sync();
        std::cin.ignore();
    }
    void ClearScreen()
    {
        HANDLE                     hStdOut;
        CONSOLE_SCREEN_BUFFER_INFO csbi;
        DWORD                      count;
        DWORD                      cellCount;
        COORD                      homeCoords = { 0, 0 };

        hStdOut = GetStdHandle(STD_OUTPUT_HANDLE);
        if (hStdOut == INVALID_HANDLE_VALUE) return;

        /* Get the number of cells in the current buffer */
        if (!GetConsoleScreenBufferInfo(hStdOut, &csbi)) return;
        cellCount = csbi.dwSize.X *csbi.dwSize.Y;

        /* Fill the entire buffer with spaces */
        if (!FillConsoleOutputCharacter(
            hStdOut,
            (TCHAR) ' ',
            cellCount,
            homeCoords,
            &count
            )) return;

        /* Fill the entire buffer with the current colors and attributes */
        if (!FillConsoleOutputAttribute(
            hStdOut,
            csbi.wAttributes,
            cellCount,
            homeCoords,
            &count
            )) return;

        /* Move the cursor home */
        SetConsoleCursorPosition(hStdOut, homeCoords);
    }
} misc;


//Handle the result from division and cout correspondingly
void Results_Handler::division(std::string inPut)
{
    if (inPut != "Error")
    {
        std::cout << inPut;
    }
    else
    {
        std::cout << "Come on, you know you can't divide by 0...";
    }
}

//Handle the result from the exponentiation and cout correspondingly
void Results_Handler::exponentiation(std::string inPut)
{
    if (inPut != "Error")
    {
        std::cout << inPut;
    }
    else
    {
        std::cout << "You can't exponentiate by negative numbers.";
    }
}

double Math_Functions::addition(double a, double b)
{
    return a + b;
}

double Math_Functions::subtraction(double a, double b)
{
    return a - b;
}

double Math_Functions::multiplication(double a, double b)
{
    return a * b;
}

void Math_Functions::division(double a, double b)
{
    //Dividing by 0 = universe explodes
    if (b == 0)
    {
        res_handler.division("Error");
    }
    else
    {
        double c = a / b;
        std::stringstream result;
        result << c;
        res_handler.division(result.str());
    }
}

void Math_Functions::exponentiation(double a, double b)
{
    //If the number you're exponentiating with is 0 the result is always 1
    if (b == 0)
    {
        res_handler.exponentiation("1");
    }
    //If you're exponentiating with 1 the result is the same number
    else if (b == 1)
    {
        std::stringstream res;
        res << a;
        res_handler.exponentiation(res.str());
    }
    else
    {
        std::stringstream res;
        res << pow(a, b);
        res_handler.exponentiation(res.str());
    }
}

int main()
{
    //Declare variables
    double a, b;
    char function;
    std::string line;

    while (true)
    {
        misc.ClearScreen();
        std::getline(std::cin, line);

        //Check if the input is empty and ignore
        if (line.empty())
        {
            continue;
        }
        //Check if the input is either 'q' or 'Q' and break loop
        else if (line[0] == 'q' || line[0] == 'Q')
        {
            break;
        }
        //Else if everything is OK extract data
        else
        {
            std::istringstream inStream(line);
            inStream >> a;
            inStream >> function;
            inStream >> b;

            //Check for bad input and print error
            if (!inStream || function != '+' && function != '-' && function != '*' &&     function != '/' && function != '^')
            {
                std::cerr << "\"" << line << "\" is invalid input";
            }
        }

        //Check what the user wants to do
        switch (function)
        {
        case '+': std::cout << math.addition(a, b); break;
        case '-': std::cout << math.subtraction(a, b); break;
        case '*': std::cout << math.multiplication(a, b); break;
        case '/': math.division(a, b); break;
        case '^': math.exponentiation(a, b); break;
        }
        misc.Pause();
    }
    return 0;
}

Answer 1

单例模式：

您的类Math_Functions、Results_Handler和Miscellaneous似乎是对单例模式的尝试(参见1和2)。声明每个类的全局实例的方法也是有效的，但是有一些缺点，而且不是很传统。

由于您的类不包含任何成员数据，而且这个类实际上只是函数的名称空间，所以我将使用一个实际的namespace，在这种情况下甚至不用考虑完整的单例实现。示例：

namespace math
{
    double addition(double, double);
    double subtraction(double, double);
    double multiplication(double, double);
    void division(double, double);
    void exponentiation(double, double);
} // namespace

然后，要访问每个函数，现在必须使用:: (命名空间解析)运算符：math::addition(a, b);

杂项提示：

• 将参数名称保存在函数原型中。这将添加到代码文档中。
• 与你的命名约定保持一致。函数/方法有PascalCase和camelCase名称。选择一个并始终如一地使用。
• 应该使用带有<cmath>前缀的完全限定名来访问pow()等来自std::的函数。即：std::pow().
• 考虑将项目拆分为几个单独的源文件。这里已经有相当多的代码要保存在同一个源文件中。理想情况下，应该将每个类放在自己的.cpp/.h对中。
• 在main末尾返回零是可选的。如果不显式执行，编译器将默认为return 0。