How to use for loop in m-function in SIMULINK for Online tuning?

Using m-function for online ILC iteration update (P-type Law), how can compute, store and update for the next cycle?

Note-Both equation are similar.

I am using ICL P-type update law (any above eq) where im calling a m-function which will take parameters into the .m file (function ILC) directly and feed it out into the PID controller. I am to iterate the whole CL system for at least 20 trials using the equation where

uk(t)/xdi'(t) is the input for the plant from the whole controller

ek(t)/ei(t+1) is the error

sum is stored in uk+1(t)/xd(i+1)(t)

L/Lambda= learning gain which can be constant of 0.04.

my codes in the ILC m-function are as follow:

   function uk1 = ILC(uk,ek)
    %#codegen
    uk1=0
    L=0.04
    uk1=uk+L*ek; 
    uk1=uk
    end

using the above codes, it works ok but i cannot confirm if the iteration is happening or no because no value is stored as array. OR do i need a for loop to iterate ILC?

function uk1 = ILC(uk,ek)
%#codegen
t=20
uk1=0
L=0.04
for n=1:1:t
uk1(n)=uk(n)+L*ek(n); 
uk1=uk(n)
end

If i do the for loop,error of 'Attempted to access element 2. The valid range is 1-1.' ERROR yields. Please can you help me with the function codes also.

How should i implement the iteration, with or without the for loop?