Exam Q: Using Enumerations

[gretty]

Hi

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

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):

#include <iostream>
#include <cmath>

using namespace std;

enum months {jan = 1, feb, mar, apr, may, jun, jul, aug, sep, oct, nov, dec};

months nextMonth(months currentMonth);

int main()
{
	months a = nov;

	nextMonth(a);

	cout << a << endl;


	return 0;
}

months nextMonth(months currentMonth)
{
	currentMonth = currentMonth + 1;
	return currentMonth;
}

[siddhant3s]

Your not catching the value return by the function.

#include <iostream>
using namespace std;
enum months {jan = 1, feb, mar, apr, may, jun, jul, aug, sep, oct, nov, dec};
months nextMonth(months& currentMonth);
int main()
{
    months a = nov;

    a=nextMonth(a);

    cout << a << endl;


    return 0;
}

months nextMonth(months &currentMonth)
{
    return months(currentMonth+jan);
}

[ArkM]

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 noimplicit int to months conversion and the assignment is not legal here.

However it's possible to convert int value to enumerator explicitly, for example:

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(13).

Fortunately, it's so easy to correct an expression in return statement...
Do it yourself ;)

[yun]

below code will work fine, may be there is a little error in syntax as i didnot follow ur code...

Months nextMonth(Months month){
   return Months((month+1)%12) ; 
}

[ArkM]

below code will work fine, may be there is a little error in syntax as i didnot follow ur code...

Months nextMonth(Months month){
   return Months((month+1)%12) ; 
}

You are on the right way, but...
Test it for November ;)

[yun]

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 :D
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.

#include <iostream>
using namespace std;
enum months {Jan = 1, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec};

months nextMonth(months currentMonth);

int main(){ 
	months a = Dec;  
	a=nextMonth(a);  
	cout << a << endl;   

	a = Nov;  
	a=nextMonth(a);  
	cout << a << endl;   

	return 0;
} 

months nextMonth(months currentMonth){   
	return months((currentMonth+1)%13);
}

[ArkM]

>i checked for Nov and for Dec
Hmm... For December the code returns a wrong answer months(0)...
Well, the right answer is:

currentMonth % 12 + 1

;)

[yun]

>i checked for Nov and for Dec Hmm... For December the code returns a wrong answer months(0)... Well, the right answer is:

currentMonth % 12 + 1

;)

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