MATLAB: To check Scalar or Not

assignment

I have debugged the code and now the Scalar test for this code is failing although I have given a provition in the 3rd line of the code to check wheather the given inputs are scalar or not.
please help!
function valid = valid_date(year,month,day)
if nargin==3
    if fix(month) && isscalar(month) && fix(day) && isscalar(day) && fix(year) && isscalar(year) && isscalar(valid_date) && year>0 && month>0 && day>0
        if mod(year,4)==0&&mod(year,100)~=0 || mod(year,400)==0&&mod(year,100)==0
            if ismember(month,[1,3,5,7,8,10,12]) && ismember(day,[1:31])
            valid=true;
            elseif month==2 && ismember(day,[1:29])
            valid=true;
            elseif ismember(month,[4,6,9,11]) && ismember(day,[1:30])
            valid=true;
            else
            valid=false;    
            end
        else
            if ismember(month,[1,3,5,7,8,10,12]) && ismember(day,[1:31])
            valid=true;
            elseif ismember(month,[4,6,9,11]) && ismember(day,[1:30])
            valid=true;
            elseif month==2 && ismember(day,[1:28])
            valid=true;
            else
            valid=false;
            end
        end
    else
    valid=false;
    end
else
valid=false;
end
Assessment result: correctVarious inputs
 Assessment result: incorrectNon-scalar
Return false if an input is not scalar...
 Assessment result: correctThe last day of every month
 Assessment result: correctRandom leap years
 Assessment result: correctRandom non-leap years
 Assessment result: correctRandom dates

Best Answer

The reason is likely because of the order you check the inputs with, e.g.:
fix(month) && isscalar(month)
%^^^^^^^^^                    what is this supposed to test for?
%             ^^^^^^^^^^^^^^  this must be tested first!
If month is non-scalar, then fix(month) will return a non-scalar value, and then this will throw an error because && does not accept non-scalar input values. If you test isscalar first, then for a non-scalar month it will return false (i.e. a scalar!) and then MATLAB does not evaluate anything that follows the &&. Read the documentation to know more:
https://www.mathworks.com/help/matlab/ref/logicaloperatorsshortcircuit.html
Note that it is unclear what your fix(...) code is supposed to achieve, but I doubt that it does anything very useful. In any case, the order should be like this:
isscalar(month) && ??? you need to decide what to put here
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