MATLAB: How to clear persistent variables from a function using only its handle

Question

For example, say I have a simple function, test1,

function test1 = test1(x,y)
persistent k
if isempty(k), k = sum(y); end
test1 = k*x*y;

which I call from another function, test0, within which I want to clear the persistent variable, k, in test1, for example,

function test0 = test0(x,y,fn)
clear fn
for i = 1:length(x)
    test0 = fn(x(i),y);
end

using

test0(1,2,@test1)

But, of course, it doesn't work, with error

Reference to a cleared variable fn.
Error in test0 (line 4)
    test0 = fn(x(i),y);

because the line

clear fn

doesn't do the job, for obvious reasons, but I don't know how to fix this.

Thanks in advance for your help.

Answer 1

Easy:

 clear(func2str(yourfunctionhandle))

Note that from a design perspective, you'd be better off with a class rather than a function that holds state, particularly if that state is controlled from different places as you're trying to do.