printing a 2D array in ocaml

I have written following code in Ocaml to print 2D array:

let string_of_float_arr l = String.concat " " (Array.map string_of_float l)let float_arr_to_string l = String.concat "\n" (Array.map string_of_float_arr l) 

I am getting error,can anyone please help me in pointing out the error