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Exam Q: Using Enumerations

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Exam Q: Using Enumerations

 
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  #1
Jun 9th, 2009
Hi

I am studying for my C++ exam coming up & I have this practice question thats confusing me?

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Given

enum months{Jan = 1, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec};

write a C++ function that takes currentMonth of type months as the parameter, and returns the next month. For example, nextMonth(Nov) should return Nov.

months nextMonth(months currentMonth)
{
//missing code
}
my attempt is (which doesn't work & I dont know why):
C++ Syntax (Toggle Plain Text) 
  1. #include <iostream>
  2. #include <cmath>
  3.  
  4. using namespace std;
  5.  
  6. enum months {jan = 1, feb, mar, apr, may, jun, jul, aug, sep, oct, nov, dec};
  7.  
  8. months nextMonth(months currentMonth);
  9.  
  10. int main()
  11. {
  12. 	months a = nov;
  13.  
  14. 	nextMonth(a);
  15.  
  16. 	cout << a << endl;
  17.  
  18.  
  19. 	return 0;
  20. }
  21.  
  22. months nextMonth(months currentMonth)
  23. {
  24. 	currentMonth = currentMonth + 1;
  25. 	return currentMonth;
  26. }
Last edited by gretty; Jun 9th, 2009 at 3:55 am.
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Re: Exam Q: Using Enumerations

 
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  #2
Jun 9th, 2009
Your not catching the value return by the function.
C++ Syntax (Toggle Plain Text) 
  1. #include <iostream>
  2. using namespace std;
  3. enum months {jan = 1, feb, mar, apr, may, jun, jul, aug, sep, oct, nov, dec};
  4. months nextMonth(months& currentMonth);
  5. int main()
  6. {
  7.     months a = nov;
  8.  
  9.     a=nextMonth(a);
  10.  
  11.     cout << a << endl;
  12.  
  13.  
  14.     return 0;
  15. }
  16.  
  17. months nextMonth(months &currentMonth)
  18. {
  19.     return months(currentMonth+jan);
  20. }
Siddhant Sanyam
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Re: Exam Q: Using Enumerations

 
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  #3
Jun 9th, 2009
It's possible to convert enumeration value to int but no an implicit reverse conversion. That's why currentMonth = currentMonth + 1 expression is wrong. More precisely, the right side is legal subexpression (treated as (int)currentMonth + 1 and has int type) but no implicit int to months conversion and the assignment is not legal here.

However it's possible to convert int value to enumerator explicitly, for example:
C++ Syntax (Toggle Plain Text) 
  1. months m = static_cast<months>(1); // = jan

It seems that return static_cast<month>(currentMonth+1) solves the problem. No, it's wrong. If currenMonth == dec, we have 13 - no months type value of static_cast<months>(13).

Fortunately, it's so easy to correct an expression in return statement...
Do it yourself
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Re: Exam Q: Using Enumerations

 
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  #4
Jun 9th, 2009
below code will work fine, may be there is a little error in syntax as i didnot follow ur code...
C++ Syntax (Toggle Plain Text) 
  1. Months nextMonth(Months month){
  2.    return Months((month+1)%12) ; 
  3. }
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Re: Exam Q: Using Enumerations

 
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  #5
Jun 9th, 2009
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Originally Posted by yun View Post
below code will work fine, may be there is a little error in syntax as i didnot follow ur code...
C++ Syntax (Toggle Plain Text) 
  1. Months nextMonth(Months month){
  2.    return Months((month+1)%12) ; 
  3. }
You are on the right way, but...
Test it for November
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Re: Exam Q: Using Enumerations

 
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Jun 9th, 2009
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Originally Posted by ArkM View Post
You are on the right way, but...
Test it for November
Bhai as i mention in my post that i didnt check the code, well Jan = 1 was the issue
thanks for resolving the logical error.

below is the update version of the program... i checked for Nov and for Dec. Every Entry work fine.
Regards.

C++ Syntax (Toggle Plain Text) 
  1. #include <iostream>
  2. using namespace std;
  3. enum months {Jan = 1, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec};
  4.  
  5. months nextMonth(months currentMonth);
  6.  
  7. int main(){ 
  8. 	months a = Dec;  
  9. 	a=nextMonth(a);  
  10. 	cout << a << endl;   
  11.  
  12. 	a = Nov;  
  13. 	a=nextMonth(a);  
  14. 	cout << a << endl;   
  15.  
  16. 	return 0;
  17. } 
  18.  
  19. months nextMonth(months currentMonth){   
  20. 	return months((currentMonth+1)%13);
  21. }
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Re: Exam Q: Using Enumerations

 
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  #7
Jun 9th, 2009
>i checked for Nov and for Dec
Hmm... For December the code returns a wrong answer months(0)...
Well, the right answer is:
C++ Syntax (Toggle Plain Text) 
  1. currentMonth % 12 + 1
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Re: Exam Q: Using Enumerations

 
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  #8
Jun 9th, 2009
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Originally Posted by ArkM View Post
>i checked for Nov and for Dec
Hmm... For December the code returns a wrong answer months(0)...
Well, the right answer is:
C++ Syntax (Toggle Plain Text) 
  1. currentMonth % 12 + 1

Ha Ha Ha................. Thanks Once Again brother for mention my mistake.
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