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Class
Class type
val length : string -> int

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

val get : string -> int -> char

String.get s n returns the character at index n in string s. You can also write s.[n] instead of String.get s n.

  • raises Invalid_argument

    if n not a valid index in s.

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

String.set s n c modifies byte sequence s in place, replacing the byte at index n with c. You can also write s.[n] <- c instead of String.set s n c.

  • raises Invalid_argument

    if n is not a valid index in s.

  • deprecated

    This is a deprecated alias of BytesLabels.set.

val create : int -> bytes

String.create n returns a fresh byte sequence of length n. The sequence is uninitialized and contains arbitrary bytes.

  • raises Invalid_argument

    if n < 0 or n > Sys.max_string_length.

  • deprecated

    This is a deprecated alias of BytesLabels.create.

val make : int -> char -> string

String.make n c returns a fresh string of length n, filled with the character c.

  • raises Invalid_argument

    if n < 0 or n > Sys.max_string_length.

val init : int -> f:( int -> char ) -> string

init n f returns a string of length n, with character i initialized to the result of f i.

  • raises Invalid_argument

    if n < 0 or n > Sys.max_string_length.

  • since 4.02.0
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 substring of s that starts at position start and has length len.

  • raises Invalid_argument

    if start and len do not designate a valid substring of s.

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

String.fill s start len c modifies byte sequence s in place, replacing len bytes by c, starting at start.

  • raises Invalid_argument

    if start and len do not designate a valid substring of s.

  • deprecated

    This is a deprecated alias of BytesLabels.fill.

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

String.blit src srcoff dst dstoff len copies len bytes from the string src, starting at index srcoff, to byte sequence dst, starting at character number dstoff.

  • raises Invalid_argument

    if srcoff and len do not designate a valid range of src, or if dstoff and len do not designate a valid range 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 mapi : f:( int -> char -> char ) -> string -> string

String.mapi f s calls f with each character of s and its index (in increasing index order) and stores the results in a new string that is returned.

  • since 4.02.0
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 leading nor trailing 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. Its inverse function is Scanf.unescaped.

val index : string -> char -> int

String.index s c returns the index of the first occurrence of character c in string s.

  • raises Not_found

    if c does not occur in s.

val index_opt : string -> char -> int option

String.index_opt s c returns the index of the first occurrence of character c in string s, or None if c does not occur in s.

  • since 4.05
val rindex : string -> char -> int

String.rindex s c returns the index of the last occurrence of character c in string s.

  • raises Not_found

    if c does not occur in s.

val rindex_opt : string -> char -> int option

String.rindex_opt s c returns the index of the last occurrence of character c in string s, or None if c does not occur in s.

  • since 4.05
val index_from : string -> int -> char -> int

String.index_from s i c returns the index of the first occurrence of character c in string s after position i. String.index s c is equivalent to String.index_from s 0 c.

  • raises Invalid_argument

    if i is not a valid position in s.

  • raises Not_found

    if c does not occur in s after position i.

val index_from_opt : string -> int -> char -> int option

String.index_from_opt s i c returns the index of the first occurrence of character c in string s after position i or None if c does not occur in s after position i.

String.index_opt s c is equivalent to String.index_from_opt s 0 c.

  • raises Invalid_argument

    if i is not a valid position in s.

  • since 4.05
val rindex_from : string -> int -> char -> int

String.rindex_from s i c returns the index of the last occurrence of character c in string s before position i+1. String.rindex s c is equivalent to String.rindex_from s (String.length s - 1) c.

  • raises Invalid_argument

    if i+1 is not a valid position in s.

  • raises Not_found

    if c does not occur in s before position i+1.

val rindex_from_opt : string -> int -> char -> int option

String.rindex_from_opt s i c returns the index of the last occurrence of character c in string s before position i+1 or None if c does not occur in s before position i+1.

String.rindex_opt s c is equivalent to String.rindex_from_opt s (String.length s - 1) c.

  • raises Invalid_argument

    if i+1 is not a valid position in s.

  • since 4.05
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 s after position start. String.contains s c is equivalent to String.contains_from s 0 c.

  • raises Invalid_argument

    if start is not a valid position in s.

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

String.rcontains_from s stop c tests if character c appears in s before position stop+1.