compilation with modules

[Francois Colonna <colonna@ccr.jussieu.fr>]

Hello

Could somebody tell me how to compile a piece of code ( "my_code.ml")  using
a module ("my_tools.ml")

Here are the files :
___ my_tools.ml ____

module My_tools =
struct
let print_a_string a_string  =
    print_string (a_string)
;;
end

and
 ___ my_code.ml ____

open My_tools
let a_string = "a string" ;;
print_a_string a_string ;;


Thanks
François Colonna