# Module StringLabels

    module StringLabels: sig .. end

String operations.

    val length : string -> int

Return the length (number of characters) of the given string.

    val get : string -> int -> char

`String.get s n` returns character number `n` in string `s`. The first character is character number 0. The last character is character number `String.length s - 1`. You can also write `s.[n]` instead of `String.get s n`.

Raise `Invalid_argument "index out of bounds"` if `n` is outside the range 0 to `(String.length s - 1)`.

    val set : string -> int -> char -> unit

`String.set s n c` modifies string `s` in place, replacing the character number `n` by `c`. You can also write `s.[n] <- c` instead of `String.set s n c`. Raise `Invalid_argument "index out of bounds"` if `n` is outside the range 0 to `(String.length s - 1)`.

    val create : int -> string

`String.create n` returns a fresh string of length `n`. The string initially contains arbitrary characters. Raise `Invalid_argument` if `n < 0` or `n > Sys.max_string_length`.

    val make : int -> char -> string

`String.make n c` returns a fresh string of length `n`, filled with the character `c`. Raise `Invalid_argument` if `n < 0` or `n >` `Sys.max_string_length`.

    val copy : string -> string

Return a copy of the given string.

    val sub : string -> pos:int -> len:int -> string

`String.sub s start len` returns a fresh string of length `len`, containing the characters number `start` to `start + len - 1` of string `s`. Raise `Invalid_argument` if `start` and `len` do not designate a valid substring of `s`; that is, if `start < 0`, or `len < 0`, or `start + len >` `StringLabels.length` `s`.

    val fill : string -> pos:int -> len:int -> char -> unit

`String.fill s start len c` modifies string `s` in place, replacing the characters number `start` to `start + len - 1` by `c`. Raise `Invalid_argument` if `start` and `len` do not designate a valid substring of `s`.

    val blit : src:string -> src_pos:int -> dst:string -> dst_pos:int -> len:int -> unit

`String.blit src srcoff dst dstoff len` copies `len` characters from string `src`, starting at character number `srcoff`, to string `dst`, starting at character number `dstoff`. It works correctly even if `src` and `dst` are the same string, and the source and destination chunks overlap. Raise `Invalid_argument` if `srcoff` and `len` do not designate a valid substring of `src`, or if `dstoff` and `len` do not designate a valid substring of `dst`.

    val concat : sep:string -> string list -> string

`String.concat sep sl` concatenates the list of strings `sl`, inserting the separator string `sep` between each.

    val iter : f:(char -> unit) -> string -> unit

`String.iter f s` applies function `f` in turn to all the characters of `s`. It is equivalent to `f s.[0]; f s.[1]; ...; f s.[String.length s - 1]; ()`.

    val iteri : f:(int -> char -> unit) -> string -> unit

Same as `String.iter`, but the function is applied to the index of the element as first argument (counting from 0), and the character itself as second argument.
Since 4.00.0

    val map : f:(char -> char) -> string -> string

`String.map f s` applies function `f` in turn to all the characters of `s` and stores the results in a new string that is returned.
Since 4.00.0

    val trim : string -> string

Return a copy of the argument, without leading and trailing whitespace. The characters regarded as whitespace are: `' '`, `'\012'`, `'\n'`, `'\r'`, and `'\t'`. If there is no whitespace character in the argument, return the original string itself, not a copy.
Since 4.00.0

    val escaped : string -> string

Return a copy of the argument, with special characters represented by escape sequences, following the lexical conventions of OCaml. If there is no special character in the argument, return the original string itself, not a copy.

    val index : string -> char -> int

`String.index s c` returns the position of the leftmost occurrence of character `c` in string `s`. Raise `Not_found` if `c` does not occur in `s`.

    val rindex : string -> char -> int

`String.rindex s c` returns the position of the rightmost occurrence of character `c` in string `s`. Raise `Not_found` if `c` does not occur in `s`.

    val index_from : string -> int -> char -> int

Same as `StringLabels.index`, but start searching at the character position given as second argument. `String.index s c` is equivalent to `String.index_from s 0 c`.

    val rindex_from : string -> int -> char -> int

Same as `StringLabels.rindex`, but start searching at the character position given as second argument. `String.rindex s c` is equivalent to `String.rindex_from s (String.length s - 1) c`.

    val contains : string -> char -> bool

`String.contains s c` tests if character `c` appears in the string `s`.

    val contains_from : string -> int -> char -> bool

`String.contains_from s start c` tests if character `c` appears in the substring of `s` starting from `start` to the end of `s`. Raise `Invalid_argument` if `start` is not a valid index of `s`.

    val rcontains_from : string -> int -> char -> bool

`String.rcontains_from s stop c` tests if character `c` appears in the substring of `s` starting from the beginning of `s` to index `stop`. Raise `Invalid_argument` if `stop` is not a valid index of `s`.

    val uppercase : string -> string

Return a copy of the argument, with all lowercase letters translated to uppercase, including accented letters of the ISO Latin-1 (8859-1) character set.

    val lowercase : string -> string

Return a copy of the argument, with all uppercase letters translated to lowercase, including accented letters of the ISO Latin-1 (8859-1) character set.

    val capitalize : string -> string

Return a copy of the argument, with the first character set to uppercase.

    val uncapitalize : string -> string

Return a copy of the argument, with the first character set to lowercase.

    type t = string

An alias for the type of strings.

    val compare : t -> t -> int

The comparison function for strings, with the same specification as `compare`. Along with the type `t`, this function `compare` allows the module `String` to be passed as argument to the functors `Set.Make` and `Map.Make`.