Question

我是c ++的新手并且正在编写“使用c ++编写原理和练习”一书

我被要求编写一个程序，将3种货币转换成美元。我已经编写了该程序，它可以完美地用于2种货币，但它不适用于第三种（欧元），我不知道为什么。

我确信这是一件非常简单的事情，我很想念，但我会很乐意帮助你！也欢迎任何对我的代码的批评。

#include <iostream>
using namespace std;

int main(){

constexpr double yen_to_dollars=0.0091;
constexpr double euro_to_dollars=1.071;
constexpr double pound_to_dollars=1.279;

double amount=1;
char currency =' ';

cout<<"please enter an amount of currency to be converted to dollars (Y, E or P):\n";
cin >> amount >> currency;


if(currency=='Y')
cout<<amount<<"Yen = " << yen_to_dollars*amount << "dollars\n";
else if(currency=='P')
cout<<amount<<"Pounds = "<<pound_to_dollars*amount << "dollars\n";
else if(currency='E')
cout<<amount<<"Euros = "<<euro_to_dollars*amount << "dollars\n";
else
cout<<"That is an invalid currency\n";

}

Answer 1

你不是在和E＆＃39; E＆＃39;正确地：else if(currency='E')＆lt; - 这指定了＆＃39; E＆＃39;到currency变量而不是比较它。

以下是固定的例子：

#include <iostream>
using namespace std;

int main(){

constexpr double yen_to_dollars=0.0091;
constexpr double euro_to_dollars=1.071;
constexpr double pound_to_dollars=1.279;

double amount=1;
char currency =' ';

cout<<"please enter an amount of currency to be converted to dollars (Y, E or P):\n";
cin >> amount >> currency;


if(currency=='Y')
cout<<amount<<"Yen = " << yen_to_dollars*amount << "dollars\n";
else if(currency=='P')
cout<<amount<<"Pounds = "<<pound_to_dollars*amount << "dollars\n";
else if(currency=='E') // < -- fixed
cout<<amount<<"Euros = "<<euro_to_dollars*amount << "dollars\n";
else
cout<<"That is an invalid currency\n";

}

不确定它是否是stackoverflow的事情，但你应该尝试很好地格式化你的代码，所以说清楚。这会好一点：

#include <iostream>
using namespace std;

int main()
{
    const double yen_to_dollars = 0.0091;
    const double euro_to_dollars = 1.071;
    const double pound_to_dollars = 1.279;

    double amount = 1;
    char currency;

    cout << "please enter an amount of currency to be converted to dollars (Y, E or P):\n";
    cin >> amount >> currency;


    if (currency == 'Y')
        cout << amount << "Yen = " << yen_to_dollars*amount << "dollars\n";
    else if (currency == 'P')
        cout << amount << "Pounds = " << pound_to_dollars*amount << "dollars\n";
    else if (currency == 'E') // < -- fixed
        cout << amount << "Euros = " << euro_to_dollars*amount << "dollars\n";
    else
        cout << "That is an invalid currency\n";
}

Answer 2

else if(currency = 'E') 将 'E'分配给currency。

比较使用==和前两种情况一样：

else if(currency == 'E')

提示：的

每当进行比较时，将rvalue（如果有的话）放在比较运算符的左侧。然后，如果您错误地为=键入==，编译器会抱怨并让您的生活更轻松。

在if-else循环中输入错误

2 个答案: