method matching : int -> beam_type
method at : time -> value_type array
method output : int -> value_type array array
+ method frequency : int array
end;;
method delay : int
method eval : beam_type -> beam_type
end;;
+
+
+class type io_type =
+ object
+ method read : string array -> beam_type
+ method write : value_type array array -> string array
+ end;;