Function doesn't print correctly

So I have to create a "lights out" game. I have to create two functions. One function "flip"

val flip : bool array array -> int -> int -> bool array array = <fun>

that given a bool matrix and two integers i, j. it negates the values(true→false, false→true) at location i, j in the matrix, as well negatingthe values on the (up to) 4 horizontally/vertically adjacent elements.

This is my code about it:

let matrixz = [|  [|true; true; false; false|];  [|false; false; true; true|];  [|true; false; true; false|];  [|true; false; false; true|]|];;let flip_matrix matrix a b =  let n = Array.length matrix in  for i = 1 to n do     let n1 = Array.length matrix in    for j = 1 to n1 do      if i = a && j = b then begin         matrix.(i).(j) <- not matrix.(i).(j);        matrix.(i+1).(j) <- not matrix.(i+1).(j);        matrix.(i).(j+1) <- not matrix.(i).(j+1);         matrix.(i).(j-1) <- not matrix.(i).(j-1);        matrix.(i-1).(j) <- not matrix.(i-1).(j);      end;    done;  done;  matrix;; 

Which I think is correct. But also I have to make another function:

val print_matrix : bool array array -> unit = <fun>

Which given a bool matrix, it prints it on screen (true →”T”, false→”F”).

This is my code about it:

let print_s matrix =  let n = Array.length matrix in  for i = 0 to n-1 do     let n1 = Array.length matrix in    for j = 0 to n1-1 do      print_string matrix.(i).(j);    done;     print_string "/n";  done;

This would be the correct output:

# flip matrix 1 4;;# print_matrix matrix;;FTFTTFFFFFTT

I know the second function is incorrect.