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 false. The name of the output argument is valid.

Hi Folks,

I have tried and ended up in errors. For example(valid_date(2018, 4, 1) failed,The last day of every month

Variable valid has an incorrect value. valid_date(2000, 1, 31) failed..., Random leap years

Variable valid has an incorrect value. valid_date(1624, 2, 29) failed..., Random dates

Variable valid has an incorrect value. valid_date(1433, 6, 28) failed...)

Kindly point out the errors I have made!

function valid = valid_date(year,month,day)
if (nargin==3)
    if (fix(valid_date)&&isscalar(valid_date))
        if((rem(year,4)==0||rem(year,400)==0) && rem(year,100)~=0)
            if((month==1||3||5||7||9||11) && 0<day<32)
            valid=true;
            elseif(month==2 && 0<day<30)
            valid=true;
            elseif((month==4||6||8||10||12) && 0<day<31)
            valid=true;
            else
            valid=false;    
            end
        else
            if((month==1||3||5||7||9||11) && 0<day<32)
            valid=true;
            elseif((month==4||6||8||10||12) && 0<day<31)
            valid=true;
            elseif(month==2 && 0<day<29)
            valid=true;
            else
            valid=false;
            end
        end
        else
        valid=false;
        end
    else
        valid=false;
    end

[Stephen Cobeldick]

Note that this syntax

month==1||3||5||7||9||11

is equivalent to:

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

which, because 11 is non-zero, will always be true. You should start thinking about using vectors, which would make that comparison easy (hint: use any)

[Guillaume]

As Stephen points out, inventing your own syntax for the if tests is not going to work very well. Note that to check if a number is a member of the set {a,b,c}, you'd use ismember(x, [a, b, c]), not some invented x==a||b||c syntax.

In this case, it didn't even matter that the comparison didn't make sense because of:

if fix(valid_date)&&isscalar(valid_date)  %removed unnecessary parentheses
    %...
end

which recurse into valid_date, this time with no argument. Since valid_date with 0 inputs always return false (thankfully, breaking the recursion), and since fix(false) is always false, the above if is always false.

As coded, the function can be simply reduced to

function valid = valid_date(~, ~, ~)
    valid = false;
end

[Rakeshwar Elango]

Thank you Stephen and Guillaume as the newly invented statement of me didn't through any error so I was wandering wheather where it went wrong. Thank you for your suggesion!

Answer 1

[James Tursa]

Looks like you are taking the same class as Rahul. Rather than repeat my answer here, I will simply direct you to the link:

https://www.mathworks.com/matlabcentral/answers/466971-if-else-problem-for-year

[Gloria Paul]

Been stuck on this assignment for awhile now. Very close to giving up