Enforce function argument validation limitations

[florianschanda]

https://www.mathworks.com/help/matlab/matlab_prog/function-argument-validation-1.html

do not use functions that interact with the function workspace. Specifically, do not use nested functions or any of the functions listed in the following table in the arguments block.

• assignin
• builtin
• clear
• dbstack
• eval
• evalc
• evalin
• exist
• feval
• input
• inputname
• load
• nargin
• narginchk
• nargoutchk
• save
• whos
• who