Whats wrong with my code,I'm not able to get though my test if the month is 12?

4. Write a function called day_diff that takes four scalar positive integer inputs, month1, day1, month2, day2. These represents the birthdays of two children who were born in 2015. The function returns a positive integer scalar that is equal to the difference between the ages of the two children in days. Make sure to check that the input values are of the correct types and they represent valid dates. If they are erroneous, return -1. An example call to the function would be >> dd = day_diff(1,30,2,1); 2 which would make dd equal 2. You are not allowed to use the built-in function datenum or datetime.

function a = day_diff(month1,day1,month2,day2)
if ((month1 && month2)==(1 || 3 || 5 || 7 || 8 || 10 || 12))
    month1 = month1*31;
    month2=month2*31;
else if ((month1 && month2)==(4 || 6 || 9 || 11))
        month1 = month1*30;
    month2=month2*30;
    else
        month1=28;
        month2=28;
    end
end
finday1=month1+day1;
finday2=month2+day2;
a=abs(finday1-finday2);
end

[Geoff Hayes]

Please provide the input values to your function that return the invalid result if one (or both?) of your months are twelve.

[John D'Errico]

Just don't do your test in December? :P

Ok, I assume that is a useless answer. But while I know that you know what you THINK this does:

((month1 && month2)==(1 || 3 || 5 || 7 || 8 || 10 || 12))

It does not do that.

Instead, learn to use the ismember function.

[Vijayramanathan B.tech-EIE-118006077]

Okay Thanks for your help John D;Errico

[Vijayramanathan B.tech-EIE-118006077]

@Geoff Hayes This was my call statement day_diff(1, 1, 12, 31)

[Geoff Hayes]

also look at

 month1 = month1*31;
 month2 = month2*31;

If month1 is 1 (January) and month2 is 12 (December), what is the intent of the above code? It is almost as if you are assuming that every month has 31 days (12*31) and then the

 a=abs(finday1-finday2);

would make sense. But that assumption is invalid...