My code keeps breaking for a few data input, Please help! The Question is: Write a function called valid_date that takes three positive integer scalar inputs year, month, day. If these three represent a valid date, return a logical true, otherwise fa

function valid = valid_date(year, month, day)
valid = false;
if isscalar(year) && year>0 && isscalar(month) && month~=0 && isscalar(day) && day>0
    if mod(year,400)==0 || (mod(year,4) == 0 && mod(year,100) ~= 0)
        if month==2
            if day <= 29
                valid = true;
            end
        elseif (month==4||month==6||month==8||month==10||month==12)
            if day<=30
                valid = true;
            end
            if day==31
                     valid =true;
                     fprintf('good\n')
             end
        elseif (month==1||month==3||month==5||month==7||month==9||month==11)
            if day<=31
                valid = true;
            end
        else
            valid = false;
        end
    else
        if month==2
            if day <= 28
                valid = true;
            end
        elseif (month==4||month==6||month==8||month==10||month==12)
            if day<=30
                valid = true;
            end
            if day==31
                    valid =false;
            end
        elseif (month==1||month==3||month==5||month==7||month==9||month==11)
            if day<=31
                valid = true;
            end
        else
            valid = false;
        end
    end
end
end

[Faris Shaikh]

The last day of every month

Variable valid has an incorrect value. valid_date(2014, 8, 31) failed...

Random dates

Variable valid has an incorrect value. valid_date(1399, 8, 31) failed...

Answer 1

[Image Analyst]

Step through it with the debugger, like we all do. If you don't know how, see this link

So when month is 8, and day is 31, what do you think this will return:

elseif (month==4||month==6||month==8||month==10||month==12)
            if day<=30
                valid = true;
            end
            if day==31
                    valid =false;
            end

Do you think it will return true or false for "valid"? All those months should have valid true if (day <= 31) && (day >= 1), not day<=30. You don't even need the next if.

elseif (month==1 || month==3 || month==5 || month==7 || month==8 || month==10 || month==12)
            if (day >= 1) && (day <= 31)
                valid = true;
            else
                valid =false;
            end

Also, I would not name variables year, month, or day since those are built-in functions.

[Faris Shaikh]

Thank you for the help!

However, the code you suggested still fails on cases:

Various inputs

valid_date(2018, 4, 31) failed...

The last day of every month

Variable valid has an incorrect value. valid_date(2007, 4, 31) failed...

Random dates

Variable valid has an incorrect value. valid_date(578, 6, 29) failed..

Also, i agree that day, month, year are not fantastic variable names but i was told to sue them so i don't mind.

[Image Analyst]

Well, I know it does. But I thought that seeing my code would make you realize that you had completely wrong days for many of the months and then you, being a bright engineer, would correct it. Sounds like homework and I'm not sure how much of your homework you're allowed to let others do for your. If you still can't figure it out let me know.

I've gotten ill-advised suggestions from people before but nobody has ever told me to sue them over it ?. Sounds a bit harsh. Maybe just an apology from them would be fine and you could avoid the litigation. ?

[Faris Shaikh]

Thank you for your resposnse, it has made me realize how at fault I am and how I need to correct me behaviour. I appreciate that you are still willing to help. I am not a computer science engineer, actuallly studying aerospace instead, and find computer programming difficult. I am better at other classes. Please forgive me for my inappropriate behaviour and thanks for the tips.