I don't understand where I'm going wrong

function valid=valid_date(year,month,day)
if nargin~=3
    valid=false;
end
if ~isscalar(year) || year<1 || year~= fix(year)
    valid=false;
elseif ~isscalar(month) || month<1 || month~= fix(month) || month>12
    valid=false;
elseif ~isscalar(day) || day<1 || day~= fix(day) || month>31
    valid=false;
end
% leap year
if mod(year,4)==0 && mod(year,100)~= 0 || mod(year,400)== 0
    if month==2 
        if ~(1<=day&&day<=29)
            valid=false;
        end
    elseif month ~= (1||3||5||7||8||10||12)
        if ~(1<=day&&day<=30)
            valid=false;
        end
    else 
        valid=true;
    end
end
if month == 2
    if ~(1<=day&&day<=28)
        valid=false;
    end
elseif month ~= (1||3||5||7||8||10||12)
    if ~(1<=day&&day<=30)
        valid=false;
    end
else
    valid=true;
end

[Dyuman Joshi]

You will need to provide more information as to what the objective is, what the inputs are, how you are calling the function and what the problem/issue is.

[Steven Lord]

I'm guessing it's related to this homework assignment that seems to get assigned early on in a lot of programming courses.

[Shruti]

hello! below is the assignment question.

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. If any of the inputs is not a positive integer scalar, return false as well. Note that every year that is exactly divisible by 4 is a leap year, except for years that are exactly divisible by 100. However, years that are exactly divisible by 400 are also leap years. For example, the year 1900 was not leap year, but the year 2000 was. Note that your solution must not contain any of the date related built-in MATLAB functions.

[Stephen23]

Note that || is a bivariate operator: it is a function with exactly two inputs and has exactly one output. You cannot chain it into arbitrarily long lists of values and expect it to operate on all of the values simultaneously. So your code:

(1||3||5||7||8||10||12)

is exactly equivalent to writing

((((((1||3)||5)||7)||8)||10)||12)

which because all of the values are non-zero is basically equivalent to

((((((true||true)||true)||true)||true)||true)||true)

which is exactly equivalent to

true

So your code

month ~= (1||3||5||7||8||10||12)

reduces down to

month ~= true

which because TRUE is equivalent to 1 your code is exactly equivalent to

month ~= 1

In short: your invented syntax does not do what you think it does and will not work.

Tip: use ISMEMBER instead. It works.

Answer 1

[Sai Teja G]

Hi Shruti,

I assume that you are facing the "not enough input arguments" error, it occurs because the function is being executed without supplying the necessary arguments; in other words, no input arguments are provided when the function is called. This is why the error appears during the evaluation of the second "if" condition. To rectify this issue, you can introduce a `return` statement at the end of the first "if" condition. Additionally, it's important to note that the variable `valid` has not been initialized prior to the check for the number of input arguments (`nargin`). If the correct number of arguments is not provided, the variable `valid` will remain undefined, potentially leading to further errors.

function valid=valid_date(year,month,day)
valid=true;
if nargin~=3
    valid=false;
    return; % exit your code if there are not enough arguments
end
if ~isscalar(year) || year<1 || year~= fix(year)
    valid=false;
elseif ~isscalar(month) || month<1 || month~= fix(month) || month>12
    valid=false;
elseif ~isscalar(day) || day<1 || day~= fix(day) || month>31
    valid=false;
end
% leap year
if mod(year,4)==0 && mod(year,100)~= 0 || mod(year,400)== 0
    if month==2 
        if ~(1<=day&&day<=29)
            valid=false;
        end
    elseif month ~= (1||3||5||7||8||10||12)
        if ~(1<=day&&day<=30)
            valid=false;
        end
    else 
        valid=true;
    end
end
if month == 2
    if ~(1<=day&&day<=28)
        valid=false;
    end
elseif month ~= (1||3||5||7||8||10||12)
    if ~(1<=day&&day<=30)
        valid=false;
    end
else
    valid=true;
end

Hope this clarifies your doubt!

[Shruti]

hi sai! the error im receiving is not related to input arguments.

>>valid=valid_date(2001,03,15)

'Output argument "valid" (and possibly others) not assigned a

value in the execution with "valid_date" function.'

This is the error im receiving, i know that my code runs okay for the leap year task so something is either undefined or going wrong for non leap year tasks but I cannot locate it. I'd appreciate more help on this. Also, the code returned false for (2018,4,31) that means the i accounted for the months with 30days but for others its still not working.

[Walter Roberson]

if month == 2
    if ~(1<=day&&day<=28)
        valid=false;
    end

If the condition does not hold, you do not set valid to true

[Shruti]

I have put else valid=true; end at the end of that loop, so why doesn't that work?