Number of days in the month

[lainalex]

So I have to code a program that will output how many days are in the month not excluding leaper year. I have placed the code below, and I unable to find the error, I am getting an error of "expression must be a modifiable lvalue". Any help would be appreciated.

#include <iostream>
using namespace std;

int main()
{
	cout << "Enter a Date to obtain how many days are in a month:" << endl;
	int year = 0;
	int month = 0;
	int days;
	cout << "Enter Year: ";
	cin >> year;
	cout << "Enter Month: ";
	cin >> month;

	
	if (month == 4 || month == 6 || month == 9 || month = 11)
		days = 30;
		
	else if (month == 02)
	{
		bool leapyear = (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0);

		if (leapyear == 0)
				days = 29;
		else 
				days = 29;
	}

	else 
	days = 31;

return days;
}

[machinafour]

Line 16: needs to be 'month == 11' instead of 'month = 11'

[machinafour]

Also, line 24 needs to be

days = 28;

otherwise every February has 29 days!

[MikeyBoy]

The error message should give you the number of the line on which the error occurs.

I can't immediately spot where that particular error is. I'm guessing it might have something to do with the way precedences are resolved in line 21, but I may be wrong. If you use more parentheses to enforce the precedence that you actually intend, then it might fix the problem. But, as I say, I'm just guessing.

I've noticed some other problems with your code:

At line 16, the month = 11 clause is, presumably, a typo for month == 11. This will cause that if condition to always evaluate to true, regardless of the initial value of month.

At line 19, using a leading in 02 instructs the compiler to consider this an octal value, rather than a decimal one. In this case, it doesn't cause a problem, as 2 in octal is the same as 2 in decimal, but it's worth taking care over it.

At line 23, it would be more idiomatic to compare a bool variable to true or false:

if (leapyear == false)

but most programmers would find the following even more idiomatic:

if (!leapyear)

Presumably line 24 is intended to be setting the number of days to 28, not 29?

EDIT: It's normal to have main return 0 for success, and a non-zero code for failure. Did you intend to write the number of days out to the standard output, rather than returning it?