Question

我正在编写一段代码，使用switch语句在Celsius和Fahrenheit之间进行转换，如下面的代码所示。

#include <stdio.h>
#include <iostream>

using namespace std;

float celsius;
float fahrenheit;

void convertF()
{
    celsius = ((fahrenheit - 32) * 5) / 9;
}

void convertC()
{
    fahrenheit = (((celsius * 9) / 5) + 32);
}

int main()
{
    unsigned short choice;

    cout << "Welcome to the temperature converter.\n";
    cout << "Please press '1' for celsius to fahrenheit conversion" << endl;
    cout << "Or, type '2' for fahrenheit to celsius conversion." << endl;
    cout << "To exit, press 0" << endl;
    cin >> choice;

    switch(choice) 
    {
        case 0:
          return 0;
          break;

        case 1:
          cout << "Please enter temperature in celsius:";

          cin >> celsius;
          convertC();

          cout << "\n";
          cout << "Computing...\n\n";
          cout << "The temperature in Fahrenheit is " << fahrenheit << ".\n";
          cout << "Press any key to terminate the program." << endl;
          cout << endl;
          break;

        case 2:
          cout << "Please enter temperature in fahrenheit:";

          cin >> fahrenheit;
          convertF();

          cout << "\n";
          cout << "Computing...\n\n";
          cout << "The temperature in celsius is " << celsius << ".\n";
          cout << "Press any key to terminate the program." << endl;
          cout << endl;
          break;    

        default:
          cout << "That is not an option!" << endl;
          cout << "Please close the program and try again." << endl;
          break;
    }

    return 0; 
}

如果用户选择1或2，程序将执行转换。然后按任意键结束程序。

但是我想在第一次转换后给他们另一次转换的机会，这样他们就可以退出程序或执行另一次转换。我试图在案例1和案例2中加入另一个switch语句，但它没有用。

解决此问题的最佳方法是什么？我在想是否有完全使用switch语句的替代方法？

Answer 1

你需要的只是用switch语句将程序的一部分包含在某种循环中。

该程序可能类似于以下内容

#include <iostream>

using namespace std;

float convertF( float fahrenheit )
{
    return ((fahrenheit - 32) * 5) / 9;
}

float convertC( float celsius )
{
    return (((celsius * 9) / 5) + 32);
}

int main()
{
    cout << "Welcome to the temperature converter.\n";

    while ( true )
    {
        cout << "\nPlease press '1' for celsius to fahrenheit conversion" << endl;
        cout << "Or, type '2' for fahrenheit to celsius conversion." << endl;
        cout << "To exit, press 0" << endl;

        unsigned short choice;

        if ( !( cin >> choice ) || ( choice == 0 ) ) break;

        switch( choice )
        {
            float celsius;
            float fahrenheit;

        case 1:
            cout << "Please enter temperature in celsius:";

            cin >> celsius;

            cout << "\n";
            cout << "Computing...\n\n";
            cout << "The temperature in Fahrenheit is " << convertC( celsius ) << ".\n";
            break;

        case 2:
            cout << "Please enter temperature in fahrenheit:";

            cin >> fahrenheit;

            cout << "\n";
            cout << "Computing...\n\n";
            cout << "The temperature in celsius is " << convertF( fahrenheit ) << ".\n";
            break;    

        default:
            cout << "That is not an option!" << endl;
            break;

        }
    }

    return 0;
}

为了更具可读性，您可以引入类似

的枚举

enum { CELSIUS = 1, FAHRENHEIT = 2 };

并将其枚举器用作案例标签。例如

switch( choice )
{
    float celsius;
    float fahrenheit;

case CELSIUS:
    //...

case FAHRENHEIT:
    //...

default:
    //...
}

Answer 2

您可以在循环中使用switch语句：

do
{
    cin >> choice;
    switch(choice)
    {
        //cases
    }
}
while (choice != 0);

或

choice = /* not 0 */;
while(choice != 0)
{
    cin >> choice;
    switch(choice)
    {
    //cases
    }
}

或

for(unsigned int choice = /* not 0 */; choice != 0; )
{
    cin >> choice;
    switch(choice)
    {
        //cases
    }
}

Answer 3

您可以像这样使用while循环：

unsigned int choice;
do
{
    cin >> choice;
    // switch with only case 1 and 2
}
while(choice != 0);
return 0;

我不知道你完全使用switch语句的替代方法是什么意思。

Answer 4

do-while循环可能是解决它的最简单方法。您想检查while(choice != 0)以继续运行循环，直到用户输入0作为选择，这意味着您希望输入部分也在do-while循环内，因为您希望进一步输入，并在do-while内也有switch语句。当choice输入为0时，循环将结束。

这显示了do-while循环的一些示例：http://www.cplusplus.com/doc/tutorial/control/

Answer 5

只需更改您的代码：

    cout << "Welcome to the temperature converter.\n";
    while(1)   // <----- Add this 
    {          // <----- Add this 
        cout << "Please press '1' for celsius to fahrenheit conversion" << endl;
        //...
        // All your code down to
        //...
       cout << "Please close the program and try again." << endl;
       break;
       }

    }  // <----- Add this 

return 0;

嵌套的Switch语句 - 返回到switch的开头

5 个答案: