`sig
exception Invalid_string
module String :
sig
val init : int -> (int -> char) -> string
val find : string -> string -> int
val find_from : string -> int -> string -> int
val split : string -> string -> string * string
val nsplit : string -> string -> string list
val join : string -> string list -> string
val slice : ?first:int -> ?last:int -> string -> string
val lchop : string -> string
val rchop : string -> string
val of_int : int -> string
val of_float : float -> string
val of_char : char -> string
val to_int : string -> int
val to_float : string -> float
val ends_with : string -> string -> bool
val starts_with : string -> string -> bool
val enum : string -> char Enum.t
val of_enum : char Enum.t -> string
val map : (char -> char) -> string -> string
val mapi : (int -> char -> char) -> string -> string
val iteri : (int -> char -> unit) -> string -> unit
val fold_left : ('a -> char -> 'a) -> 'a -> string -> 'a
val fold_right : (char -> 'a -> 'a) -> string -> 'a -> 'a
val explode : string -> char list
val implode : char list -> string
val strip : ?chars:string -> string -> string
val exists : string -> string -> bool
val replace_chars : (char -> string) -> string -> string
val replace : str:string -> sub:string -> by:string -> bool * string
val trim : string -> string
val uppercase_ascii : string -> string
val lowercase_ascii : string -> string
val capitalize_ascii : string -> string
val uncapitalize_ascii : string -> string
val split_on_char : char -> string -> string list
val length : string -> int
val get : string -> int -> char
val set : ExtBytes.Bytes.t -> int -> char -> unit
val create : int -> ExtBytes.Bytes.t
val make : int -> char -> string
val copy : string -> string
val sub : string -> int -> int -> string
val fill : ExtBytes.Bytes.t -> int -> int -> char -> unit
val blit : string -> int -> ExtBytes.Bytes.t -> int -> int -> unit
val concat : string -> string list -> string
val iter : (char -> unit) -> string -> unit
val escaped : string -> string
val index : string -> char -> int
val index_opt : string -> char -> int option
val rindex : string -> char -> int
val rindex_opt : string -> char -> int option
val index_from : string -> int -> char -> int
val index_from_opt : string -> int -> char -> int option
val rindex_from : string -> int -> char -> int
val rindex_from_opt : string -> int -> char -> int option
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 : ExtString.String.t -> ExtString.String.t -> int
val equal : ExtString.String.t -> ExtString.String.t -> bool
val to_seq : ExtString.String.t -> char Stdlib.Seq.t
val to_seqi : ExtString.String.t -> (int * char) Stdlib.Seq.t
val of_seq : char Stdlib.Seq.t -> ExtString.String.t
external unsafe_get : string -> int -> char = "%string_unsafe_get"
val unsafe_set : ExtBytes.Bytes.t -> int -> char -> unit
val unsafe_blit :
string -> int -> ExtBytes.Bytes.t -> int -> int -> unit
val unsafe_fill : ExtBytes.Bytes.t -> int -> int -> char -> unit
end
end`