val failwithf : ('a, unit, string, 'b) format4 -> 'a
(** Like [failwith] but supports printf-like arguments. *)
+val isspace : char -> bool
+(** Return true if char is a whitespace character. *)
+
+val isalnum : char -> bool
+(** Return true if char is an alphanumeric character. *)
+
val files_equal : string -> string -> bool
(** [files_equal filename1 filename2] returns true if the files contain
the same content. *)