`sig external length : string -> int = "%string_length" external get : string -> int -> char = "%string_safe_get" external set : bytes -> int -> char -> unit = "%string_safe_set" external create : int -> bytes = "caml_create_string" val make : int -> char -> string val init : int -> f:(int -> char) -> string val copy : string -> string val sub : string -> pos:int -> len:int -> string val fill : bytes -> pos:int -> len:int -> char -> unit val blit : src:string -> src_pos:int -> dst:bytes -> dst_pos:int -> len:int -> unit val concat : sep:string -> string list -> string val iter : f:(char -> unit) -> string -> unit val iteri : f:(int -> char -> unit) -> string -> unit val map : f:(char -> char) -> string -> string val mapi : f:(int -> char -> char) -> string -> string val trim : string -> string val escaped : string -> string val index : string -> char -> int val rindex : string -> char -> int val index_from : string -> int -> char -> int val rindex_from : string -> int -> char -> int val contains : string -> char -> bool val contains_from : string -> int -> char -> bool val rcontains_from : string -> int -> char -> bool val uppercase : string -> string val lowercase : string -> string val capitalize : string -> string val uncapitalize : string -> string type t = string val compare : StringLabels.t -> StringLabels.t -> int external unsafe_get : string -> int -> char = "%string_unsafe_get" external unsafe_set : bytes -> int -> char -> unit = "%string_unsafe_set" external unsafe_blit : src:string -> src_pos:int -> dst:bytes -> dst_pos:int -> len:int -> unit = "caml_blit_string" [@@noalloc] external unsafe_fill : bytes -> pos:int -> len:int -> char -> unit = "caml_fill_string" [@@noalloc] end`