Is calendar date valid

[laurisplus]

Is this code the right way to tell if the data is valid? It tried to take into account long years and short years which makes February 28 or 29 days long.

  #include <iostream>
using namespace std;

int main()
{
int year;
int date;
int month;

cout << "Enter the year, the number of month and date please! " << endl;
cin >> year;
cin >> month;
cin >> date;

if (year / 4 %0){

if (month = 1||3||5||7||9||11){
    if (date >=1){
    if (date <=31){
        cout << "The date is valid";
    }
}
}
else if (month = 4,6,8,10,12){
    if (date >=1){
    if (date <=30){
        cout << "The date is valid";
    }
}
}
else if (month = 2){
    if (date >=1){
    if (date <=29){
        cout << "The date is valid";
    }
}
}
} else if (year/4 !=0){
if (month = 1||3||5||7||9||11){
    if (date >=1){
    if (date <=31){
        cout << "The date is valid";
    }
}
}
else if (month = 4,6,8,10,12){
    if (date >=1){
    if (date <=30){
        cout << "The date is valid";
    }
}
}
else if (month = 2){
    if (date >=1){
    if (date <=28){
        cout << "The date is valid";
    }
}
}
}



    return 0;
}

[gofurbek]

i think this code will crush when you run it.

change this code:

if (year / 4 %0){

to
if (year % 4 == 0)

and try to optimize the code, there are too many if else statements.

but idea is good.

[andywestken]

(1) Wayward code!

if (month = 1||3||5||7||9||11){

is not right at all!

Firstly, = is for assignment whereas == is for comparison (this error is all over your code!)

And secondly, to test 'month' against multiple values you need to compare it against each number in turn (with ==) and then || the results of all the comparisons (this error is also repeated.)

if ((month == 1) || (month == 3) || // etc

(you don't need the extra brackets here, but I find it makes it easier to read.)

This (fixing the comparison operator)

if (month == 1||3||5||7||9||11){

is or-ing the result of the comparison month == 1 with the values 3, 5, ... (which are all equal to true as they are non-zero.) So this test will always evaluate to true, whatever the value of 'month'. It pretty much looks like this to the compiler:

if ((month == 1) || true || true || true || true || true){

(The original code is setting month to the value 1 (which is true) and then or-ing that with true; so the if statement will always evaluate to true.)

And this line is even worse (why , this time rather than || ??)

else if (month = 4,6,8,10,12){

See "Comma operator" section on this page.
http://www.cplusplus.com/doc/tutorial/operators/

(This will also always evaluate to true.)

(2) Misplaced code?

I think you're testing for leap years at the wrong place, which ends up with you duplicating code. (How many months are affected by leaping?)

(3) Incomplete code.

Testing for leap years is a little bit trickier than checking if the year is divisible by four.

* Leap Years are any year that can be evenly divided by 4 (such as 2012, 2016, etc)
* except if it can can be evenly divided by 100, then it isn't (such as 2100, 2200, etc)
* except if it can be evenly divided by 400, then it is (such as 2000, 2400)

https://www.mathsisfun.com/leap-years.html

(4) Extra code?

You could also use && here? (Instead of nested if statements.)

    if (date >=1){
    if (date <=31){
        cout << "The date is valid";
        }
   }

Have you used arrays yet? If so, think how you could use one to squash your implementation down further.

Andy

PS The indenting in your code is a bit off, which makes it that bit harder to read.

[Duthomhas]

A month number must always be in the range [1,12]. If it is not, then the date is invalid.

Any year is valid. But you do need a function to tell you whether a given year is a leap year or not. Use the logic given to you by andywestken.

Now you can check the day of the month. There is a pattern.
For February (month 2), the number of days in the month is (28 + is it a leap year?).
For months numbered less than 8, the number of days is (30 + is month number odd?)
For all remaining months the number of days is (31 - is month number odd?).

Hope this helps.