MATLAB: BUG in nargin < 3

MATLABnargin bug r2018b

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

Best Answer

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

Related Solutions

MATLAB: Function with mismatched inputs

Yes, declaring extra input arguments is fine, as long as the code does not use any argument that is not passed. The nargin() call helps determine how many arguments were actually passed, and you can use exist() to determine whether an individual parameter was passed.

MATLAB: Nargin

nargin means "number of arguments in". In the above code it looks pretty useless:

if nargin < 2
  %do stuff
end

nargin in this case can only be 0 or 1, since yatzy(n) only allows for one input argument, (n), or no input arguments, yatzy. If you call yatzy with two input arguments, e.g.

yatzy(4,5)

It will error out with something along the lines of "Error using yatzy, more input arguments than expected"

Now as for future reference, since you're learning: nargin is typically used for error checking and so you can have optional arguments, e.g:

let's write a program f that takes one or two input arguments with the 2nd being optional:

function out = f(x,y);
if nargin==0
  %user called >>f
  error('Not enough input arguments, 1 is required');
elseif nargin==1
  %user called f(x)
  y = pi;
end  %if neither, user called f(x,y)

Here we've made sure the person enters at least one argument, x, if they entered a second one great! if not, the second one, y, = pi.

Good luck!

Best Answer

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MATLAB: Function with mismatched inputs

MATLAB: Nargin

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