Update a variable within a function and recalculate

I have created the following function

function y=fun(x)
y=2*x;
if y<0
        x=-x    
end

and I would like to update the input argument x if x is negative so then it invokes again the function. How can I do that?

Answer 1

[Iain]

once you invert x, add the line...

y = fun(x);

[Giorgos Papakonstantinou]

Thank you lain. I knew already that I could do that but I was wondering if there is any other solution. I would appreciate if you could suggest any other possible solutions.

[Iain]

Theres a few things you can do.

I recommend, wherever possible, making sure that the input is correct before even getting to the actual business code. In this case x = abs(x);

Where that isn't possible, you can repeatedly call the function like that. And the last option is to place a while loop around your business code.

answer_invalid = true; keep_trying = true;

while keep_trying & answer_invalid

%business code here:

do some checks on the answer to see if it is valid, and update answer_invalid as needed. do some checks to make sure you haven't gotten stuck in an infinite loop and set keep_trying to false if so.

end

[Giorgos Papakonstantinou]

lain I made a new question related to my question here. Check in here http://www.mathworks.com/matlabcentral/answers/76640-two-functions-in-the-same-file-causing-error-maximum-recursion-limit-of-500-reached