L'hopital rule doesn't work?

I'm making an application to use l'hopital's rule. When I use this function, nothing comes up for it. Why so?

function y=mylhopital(f,g) %f&g are function handles

syms x

while(limit(f,x,0)==0 & limit(g,x,0)==0) %When the limit of f(x) and g(x) approaches to zero and the value is both zero

f=diff(f(x)); %Differentiate f with respect to x

g=diff(g(x)); %Differentiate g with respect to x

end

y=limit(f,x,0)/limit(g,x,0);

Answer 1

[Matt J]

You didn't assign diff(f(x)) and diff(g(x)) to anything.