在循环C++中切换语句

Question

试图编写一个程序来计算盒子的体积,表面积或"周长".我希望能够为每个主题输入一个字母,然后在计算该主题后,输入下一个主题的字母.该程序还希望在键入Q时结束.我相信我的数学是正确的,但这个程序对我不起作用.它编写得很好,但音量根本不会计算,尽管其他两个主题会.我还得到了三行答案,当我输入第二个字母作为第二个值时,程序就疯了.任何和所有的帮助非常感谢.谢谢你的时间.

include <iostream>
include <iomanip>

using namespace std;

const char SENTINEL = 'Q';//found this suggestion online to quit a program

int main ()
{

char V, A, G, inputChar;
float length, width, depth, totalV, totalA, totalG;

cout<<"Enter character V for Volume, character A for Surface Area,\n";
cout<<"character G or Girth plus Depth or Q to quit\n"<<endl;
cin>>inputChar;// pick letter
while (inputChar!=SENTINEL)// if not Q then check the if-ele statments
{
      switch (inputChar)
      case 'V':
      {
                cout<<"Enter Length, Width, and Depth for Volume\n";
                cin>>length, width, depth;
                totalV=length*width*depth;//math for volume
                cout<<"The Volume = "<<totalV<<endl;
                break;
      }
      case 'A':
      {
               cout<<"Enter Length, Width, and Depth for Surface Area\n";
               cin>>length, width, depth;
               totalA=2*length*width+2*width*depth+2*length*depth;//math for area
               cout<<"The Surface Area = "<<totalA<<endl;
               break;
      }
      case 'G':
      {
               cout<<"Enter Length, Width, and Depth for Girth\n";
               cin>>length, width, depth;
               totalG=2*(length+width)+depth;//math for girth
               cout<<"The Girth = "<<totalG<<endl;
               break;
      }          
}
      system ("pause");
      return 0;
}

Answer 1

除了Elliot的回答,我发现你的程序有一些改进,没有它我不认为它会编译.像include语句中的'#'和错误的开关块一样.即使输入多个值,我们也需要级联>>而不是逗号.

这是一个可以编译的代码:

#include <iostream>
#include <iomanip>

using namespace std;

const char SENTINEL = 'Q';//found this suggestion online to quit a program

int main ()
{

char V, A, G, inputChar;
float length, width, depth, totalV, totalA, totalG;

cout<<"Enter character V for Volume, character A for Surface Area,\n";
cout<<"character G or Girth plus Depth or Q to quit\n"<<endl;
cin>>inputChar;// pick letter

while (inputChar!=SENTINEL)// if not Q then check the if-ele statments
{
      switch (inputChar)
      {
         case 'V':

                cout<<"Enter Length, Width, and Depth for Volume\n";
                cin>>length>>width>>depth;
                totalV=length*width*depth;//math for volume
                cout<<"The Volume = "<<totalV<<endl;
                break;

         case 'A':

               cout<<"Enter Length, Width, and Depth for Surface Area\n";
               cin>>length>>width>>depth;
               totalA=2*length*width+2*width*depth+2*length*depth;//math for area
               cout<<"The Surface Area = "<<totalA<<endl;
               break;

         case 'G':

               cout<<"Enter Length, Width, and Depth for Girth\n";
               cin>>length>>width>>depth;
               totalG=2*(length+width)+depth;//math for girth
               cout<<"The Girth = "<<totalG<<endl;
               break;
      }

   cout<<"Enter character V for Volume, character A for Surface Area,\n";
   cout<<"character G or Girth plus Depth or Q to quit\n"<<endl;
   cin>>inputChar;// pick letter          
}
      return 0;
}

Answer 2

写

while ( cin >> inputChar && inputChar != SENTINEL )
{
//... 

代替

cin>>inputChar;// pick letter
while (inputChar!=SENTINEL)// 

你也可以写

auto prompt = []
{
    cout << "\nEnter character V for Volume, character A for Surface Area,\n";
    cout << "character G or Girth plus Depth or Q to quit\n"<<endl;
};

while ( prompt(), cin >> inputChar && inputChar != SENTINEL )
{
//... 

要么

auto prompt = []
{
    cout << "\nEnter character V for Volume, character A for Surface Area,\n";
    cout << "character G or Girth plus Depth or Q to quit\n"<<endl;
};

prompt();
while ( cin >> inputChar && inputChar != SENTINEL )
{
    switch (inputChar)
    {
    case 'V':
    {
    //...
    }

    //...
    }

    prompt();
}