BUG in nargin < 3

Hej, I am trying to build a function with control over 3 arguments. However, I have detected a possible bug on R2018b.

The nargin control works perfectly for any number but 3!

Here you are a minimal example.

function y = myfunction(x1,x2,x3)
    if nargin < 3
        x3=false;
        if nargin < 2
            x2 = 0;
        end
        y = x1 + x2;
        if x3
            y = y/norm(y);
        end
    end
end

Answer 1

[per isakson]

The example works as expected for me. It throws an error because no value is assigned to y

>> y = myfunction( 1, 2, true )
Output argument "y" (and maybe others) not assigned during call to "myfunction". 

There is no else clause of the outer if-statement.

/R2018b

Answer 2

[John D'Errico]

How is this a bug? Well, a bug in your code.

What do you expect to happen for 3 arguments? We see this test:

if nargin < 3

So if nargin ==3, then NOTHING inside the if executes. But that if statement controls the entire code inside your function.

Therefore the problem is when you call the function with 3 arguments, the output argument will never even be defined.

That is not a bug in MATLAB however. Not in any version of MATLAB.

[Aldo Díaz]

Sorry John for not being so good as you wished, but please don't go online crucifying people!