如何允许用户输入数字和运算符

Question

我将如何添加一个允许用户输入 2 + 2 或 10/5 之类的函数，然后简单地运行对象来计算它，就像他们使用我的"输入第一个输入"语句手动输入它时一样。因此，作为作业的一部分，我需要允许用户在控制台中输入类似 10/5 + 1/2 的内容。我还需要能够允许运算符重载，但我不确定我的程序当前是否允许这样做。任何帮助将不胜感激。谢谢！

#include <iostream>
#include <conio.h>
using namespace std;
class Rational
{
    private:
        float numInput;
    public:
        Rational(): numInput(0)
        {}
        void getValues()
        {           
            cout << "Enter number: ";
            cin >> numInput;
        }
        void showValues()
        {
            cout << numInput << endl;
        }
        Rational operator + (Rational) const;
        Rational operator - (Rational) const;
        Rational operator * (Rational) const;
        Rational operator / (Rational) const;
};
Rational Rational::operator + (Rational arg2) const
{
    Rational temp;
    temp.numInput = numInput + arg2.numInput;
    return temp;
}
Rational Rational::operator - (Rational arg2) const
{
    Rational temp;
    temp.numInput = numInput - arg2.numInput;
    return temp;
}
Rational Rational::operator * (Rational arg2) const
{
    Rational temp;
    temp.numInput = numInput * arg2.numInput;
    return temp;
}
Rational Rational::operator / (Rational arg2) const
{
    Rational temp;
    temp.numInput = numInput / arg2.numInput;
    return temp;
}
int main()
{
    Rational mathOb1, mathOb2, outputOb;
    int choice;
    mathOb1.getValues();
    cout << "First number entered: ";
    mathOb1.showValues();
    cout << endl;
    cout << "Enter operator: + = 1, - = 2, * = 3, / = 4  ";
    cin >> choice;
    cout << endl;
    mathOb2.getValues();
    cout << "Second number entered: ";
    mathOb2.showValues();    cout << endl;
    switch (choice)
    {
        case 1:
            outputOb = mathOb1 + mathOb2;
            break;
        case 2:
            outputOb = mathOb1 - mathOb2;
            break;
        case 3:
            outputOb = mathOb1 * mathOb2;
            break;
        case 4:
            outputOb = mathOb1 / mathOb2;
            break;
        default:
            cout << "Invalid choice! " << endl;
    }
    cout << "Answer: ";
    outputOb.showValues();
    cout << endl;
    return 0;
}

Answer 1

你不能使用 cin >> {int} ，如果你提供一个char，那只会失败，你会从那里卡住。

只需使用 std::getline 并从那里解析出令牌：

std::string expression;
std::getline(std::cin, expression);

然后，您可以使用许多方法中的任何一种将string拆分为标记，如此问题中所述，并循环访问令牌并根据它们是运算符还是数字来解释它们。