MATLAB: Check which output arguments are requested within a function

Question

I have a custom function that returns multiple arguments, say:

    function [arg1, arg2, arg3, arg4] = myfun(x,y,z)
     % Code
    end

Now, we can call that function e.g. in such way:

    [A, B, ~, D] = myfun(3,2,1)

If we make such call, no value has to be assigned to variable arg3 within myfun. I want to know if there is a way to check within the function body which output arguments have been called (same as arg1, arg2, arg4 above), and which outputs have been neglected (i.e. arg3 which is called with tilde).

There is a number of functions dealing with i/o arguments, but I haven't been able to find a solution to this question in the documentation of 2015a version.

Answer 1

Currently there is no inbuilt way to detect this:

https://www.mathworks.com/matlabcentral/newsreader/view_thread/325735.html

https://www.mathworks.com/matlabcentral/answers/176207-mex-and-matlab-check-if-an-output-is-skipped-unused-i-e-marked-with-tilde

Although it would be possible with some extremely inefficient and non-robust file parsing, e.g.:

https://stackoverflow.com/questions/19498911/how-to-determine-if-an-output-of-a-function-call-is-unused-matlab