c++ - 开关和功能

Question

当我运行程序并选择 premium 时，它会运行它，然后它还会运行常规服务的功能。问题出在 int main 上。我做错了什么？ IT 说我没有足够清楚地解释问题，不知道为什么，所以这里有更多的文字来解决这个问题。

premiumserv = premserv(daymin, nightmin); 
regularserv = regserv ();

完整代码如下

/************************************************/
/* Author:     Sam LaManna                      */
/* Course:     CSC 135 Lisa Frye                */
/* Assignment: Program 3 Cell Phone Bill        */
/* Due Date:   10/20/2011                       */
/* Filename:   program3.cpp                     */
/* Purpose:    This program calculates and      */
/*             prints the bill for a cellular   */
/*             telephone company                */
/************************************************/



//TODO:
//Fix account number issue: large numbers cause intfinte loop. Maybe use string?
//Complete premium and regular service calculation functions
//Output function - Figure out how to print 



#include <iostream>    //Basic input/output
#include <iomanip>     //Manipulators 

using namespace std;

void instruct();       //Function declaration for printing instructions
int accnum ();         //Function declaration for account number
char servcode ();      //Function declaration for service code
float regserv ();      //Function declaration for regular service
float premserv (int& daymin, int& nightmin);     //Function declaration for premium service
void output (float premiumserv, float regularserv);        //Function declaration for printing results

int main()
{
  int accountnum = 0;     //Var for account number
  char servicecode = 'a';     //Var for service code
  float premiumserv = 0;      //Var for premium service total
  float regularserv = 0;      //Var for regular service total
  int daymin = 0;
  int nightmin = 0;

  instruct();     //Function call to print instructions

  accountnum = accnum();     //Function call to input account number

  servicecode = servcode();  //Function call to get service code

  switch(servicecode)        //Switch to determine which calc to use
    {
    case 'r':
      break;
    case 'R':
     regserv ();
      break;
    case 'p':
      break;
    case 'P':
     premserv (daymin, nightmin);
      break;
    }

  premiumserv = premserv ( daymin, nightmin);     //Function call for regular service

   regularserv = regserv ();      //Function call for premium service

  cout <<"total" << premiumserv <<"day" << daymin << "night " << nightmin;

  return 0;
}



/************************************************/
/* Name: instruct                               */
/* Description: Prints instructions to user     */
/* Parameters: N/A                              */
/* Return Value: N/A                            */
/************************************************/

void instruct()
{
  cout << "\n" <<  "This program will calculate the cellular telephone bill for a given customer when " << "\n" 
       << "given the correct inputs. ";
  //Prints instructions to user

  return;
}

/************************************************/
/* Name: accnum                                 */
/* Description: Get user account number         */
/* Parameters: N/A                              */
/* Return Value: accnum                         */
/************************************************/

int accnum()
{
  int accnum = 0;                               //Define var for account number
  char accyn = 'n';                             //Define char for user verify
  int i = 1;                                    //Define var for sentinel loop


  do {
    cout << "\n" << "\n" << "Please enter your account number: ";
    cin >> accnum;
    while ((accnum < 0) && (i<3))
      {
    cout << "\n" << "Error - invalid number, please try again.";
    cout << "\n" << "Please enter your account number: ";
    cin >> accnum;
    i++;
    if (i == 3)
      {
        cout << "\n" << "Too many invalid attempts, program terminating." << "\n"
         << "Have a nice day. " << "\n" << "\n";
        exit (0);
      }     //end if
      }     //end while
    cout << "\n";
    cout << "Your account number is: " << accnum << "\n"
     << "Is this correct? [y/n] ";
    cin >> accyn;
  } while (accyn != 'y');     //end do/while loop


  return accnum;
}

/************************************************/
/* Name: servcode                               */
/* Description: Get service type                */
/* Parameters: N/A                              */
/* Return Value: servcode                       */
/************************************************/

char servcode()
{
  char servcode = 'a';                             //Define var for service code
  char serviceyn = 'n';                            //Define var for user verify
  int i = 1;                                       //Define var for sentinel loop

  do {
    cout << "\n" << "Please enter your service code, [R]egular or [P]remium:" << "\n";
    cin >> servcode;
    while ((servcode != 'R' && servcode != 'P' && servcode != 'r' && servcode != 'p' ) && (i < 3))
      {
    cout << "\n" << "Error - invalid service code, please try again. ";
    cout << "\n" << "Please enter your service code: ";
    cin >> servcode;
    i++;
    if (i == 3)
      {
        cout << "\n" << "Too many invalid attempts, program terminating." << "\n"
         << "Have a nice day. " << "\n" << "\n";
        exit (0);
      }     //end if
      }     //end while
    cout << "\n" << "You entered: " << servcode << "\n"
     << "Is that correct? [y,n]";
    cin >> serviceyn;
      } while (serviceyn != 'y'); // end do/while loop

  return servcode;
}

/************************************************/
/* Name: regserv                                */
/* Description: Calculations for regular serv   */
/* Parameters: N/A                              */
/* Return Value: regserv                        */
/************************************************/

float regserv ()
{
  int regmin = 0;     //Var for number of minutes used
  float regserv = 0;  //Var for cost for regular service


  cout << "\n" "Please enter the minutes used: " << "\n";
  cin >> regmin;
  regserv = (regmin - 50) * 0.2 + 10;

  return regserv;

}

/************************************************/
/* Name: premserv                               */
/* Description: Calculations for premium serv   */
/* Parameters: N/A                              */
/* Return Value: premserv                       */
/************************************************/

float premserv (int& daymin, int& nightmin)
{
   float daytotal = 0;     //Var for day total
  float nighttotal = 0;   //Var for night total
  float premserv = 0;     //Var for premium service cost

  cout << "\n" << "Please enter the number of minutes used durring the day (6AM - 6PM): " << "\n";
  cin >> daymin;
  cout << "\n" << "Please enter the number of minutes used durring the night (6PM - 6AM): " << "\n";
  cin >> nightmin;

  daytotal = (daymin - 75) * 0.1;
  nighttotal = (nightmin - 100) * 0.05;
  premserv = 25 + daytotal + nighttotal;

  return premserv;

}

Answer 1

您在 switch 语句中调用了 regserv() 或 premserv()，但是您在切换后立即无条件地调用了它们。

关于 switch 的评论表明您误解了 switch 的语义。它不会“选择”接下来要发生的事情，它实际上是在开关内部运行代码，因此您不需要在开关之后调用它们。但是，不要忘记分配 premiumserv 和 regularserv 变量并在 switch 语句中执行输出，例如:

...
case 'R':
    regularserv = regserv();
    cout << ... regularserv ...
    break;
...