sig
type ('a, 'b) t =
src:'a -> src_pos:int -> dst:'b -> dst_pos:int -> len:int -> unit
val string_string : (string, string) Make_substring.??.t
val bigstring_string :
(Make_substring.bigstring, string) Make_substring.??.t
val string_bigstring :
(string, Make_substring.bigstring) Make_substring.??.t
val bigstring_bigstring :
(Make_substring.bigstring, Make_substring.bigstring) Make_substring.??.t
end