I am having problems with my homework:Write a function called valid_date that takes three positive integer scalar inputs year, month, day....

I am trying the next code, and it run. But when i submit 'various inputs' failed, someone could help me please?

function valid = valid_date(year, month, day)
if (nargin == 3)
    if((isscalar(year) && isscalar(month) && isscalar(day)) && (year==fix(year) && month==fix(month) && day==fix(day)))
        if (rem(year,4)==0 && rem(year,100)~=0) || (rem(year,400)==0 && rem(year,100)~=0)
           if (ismember(month,[1,3,5,7,8,10,12]) && ismember(day,[1:31]))
            valid=true;
           elseif ismember(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,[2]) && ismember(day,[1:28])
                valid=true;
            elseif (ismember(month,[4,6,9,11]) && ismember(day,[1:30]))
                valid=true;
            else
                valid=false;
            end
        end  
    else
        valid=false;
    end
else
    valid= false;
end

[per isakson]

Yes, it's a bt tricky to get nested complicated if-statement right.

Are there restriction regarding use of certain Matlab functions, e.g. eomday()?

Before trying to fix the problems see: Debug a MATLAB Program

[Stephen23]

"...But when i submit 'various inputs' failed,"

Can you provide us with the cases for which the test failed?

[Abhishek Kumar]

% This is the working code
function [valid] = valid_date(y, m, d)
t = isscalar(y) && isscalar(m) && isscalar(d)
if t ~= 1
    valid = false;
else nargin == 3 && (y && m > 0) 
      
  p = rem(y,4);
  q = rem(y,100);
  r = rem(y,400);
  
  if (p == 0 && q ~= 0) || r == 0
      if (m == 1 || m == 3 || m == 5 || m == 7 || m == 8 || m == 10 || m == 12) && (d > 0 && d <= 31)
          valid = true;
      elseif (m == 4 || m == 6 || m == 9 || m == 11) && (d > 0 && d <= 30)
          valid = true;
      elseif m == 2 && (d > 0 && d <= 29)
          valid = true;
      else
          valid = false;
      end
  else
      if (m == 1 || m == 3 || m == 5 || m == 7 || m == 8 || m == 10 || m == 12) && (d > 0 && d <= 31)
          valid = true;
      elseif (m == 4 || m == 6 || m == 9 || m == 11) && (d > 0 && d <= 30)
          valid = true;
      elseif m == 2 && (d > 0 && d <= 28)
          valid = true;
      else
          valid = false;
      end
  end
  end

Answer 1

[per isakson]

Replace

(rem(year,4)==0 && rem(year,100)~=0) || (rem(year,400)==0 && rem(year,100)~=0)

by

(rem(year,4)==0 && rem(year,100)~=0) || (rem(year,400)==0)

It looks like copy&paste error.

A small test

foo = @(year) (rem(year,4)==0 && rem(year,100)~=0) || (rem(year,400)==0 && rem(year,100)~=0);
>> foo(2000)
ans =
  logical
   0
>> foo(1900)
ans =
  logical
   0
>> leap = @(year) (rem(year,4)==0 && rem(year,100)~=0) || (rem(year,400)==0);
>> leap(1900)
ans =
  logical
   0
K>> leap(2000)
ans =
  logical
   1

IMO: Here is a function that is simpler to read and understand

function valid = valid_date_poi( year, month, day )
    % What is worst an early return or an if-statement that spans thirty lines of code?
    % I think it's ok to sometimes use early returns.
    % Copyright 2020 poi
    
    if not( nargin == 3 )
        valid = false;
        return                  %   RETURN
    end
    
    is_whole_number = @(num) rem(num,1) == 0; 
    if not( isscalar(year)     && is_whole_number(year)  && year  >= 0  ...
            && isscalar(month) && is_whole_number(month) && month >= 1  ...
            && isscalar(day)   && is_whole_number(day)   && day   >= 1  )
        valid = false;
        return                  %   RETURN
    end
    
    if month >= 13
        valid = false;
        return                  %   RETURN
    end
    
    if day > eomday( year, month )  % Search Documentation for "leap year"
        valid = false;
        return                  %   RETURN
    end
    
    valid = true;
end

[Mileyka Bustamante]

Oh thank you very much!! It was a problem with leap years! You are right, I must practice with debug function a little more!