NAME

       String - String operations.

Module

       Module   String

Documentation

       Module String
        : sig end

       String operations.

       A  string  is  an  immutable  data  structure  that  contains  a  fixed-length sequence of
       (single-byte) characters. Each character can be accessed  in  constant  time  through  its
       index.

       Given  a  string s of length l , we can access each of the l characters of s via its index
       in the sequence. Indexes start at 0 , and we will call an index valid in  s  if  it  falls
       within  the range [0...l-1] (inclusive). A position is the point between two characters or
       at the beginning or end of the string.  We call a position valid in s if it  falls  within
       the  range  [0...l] (inclusive). Note that the character at index n is between positions n
       and n+1 .

       Two parameters start and len are said to designate a valid substring of s if len >= 0  and
       start and start+len are valid positions in s .

       Note:  OCaml  strings  used to be modifiable in place, for instance via the String.set and
       String.blit functions described below. This usage is only possible when  the  compiler  is
       put  in  "unsafe-string"  mode  by  giving  the  -unsafe-string  command-line option. This
       compatibility mode makes the types string and bytes (see module Bytes ) interchangeable so
       that  functions  expecting  byte sequences can also accept strings as arguments and modify
       them.

       The  distinction  between  bytes  and  string  was  introduced  in  OCaml  4.02,  and  the
       "unsafe-string"  compatibility  mode was the default until OCaml 4.05. Starting with 4.06,
       the compatibility mode is opt-in; we intend to remove the option in the future.

       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 .

       Raise Invalid_argument if n not a valid index in s .

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

       Deprecated.  This is a deprecated alias of Bytes.set .

       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 .

       Raise Invalid_argument if n is not a valid index in s .

       val create : int -> bytes

       Deprecated.  This is a deprecated alias of Bytes.create .

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

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

       String.init  n f returns a string of length n , with character i initialized to the result
       of f i (called in increasing index order).

       Raise Invalid_argument if n < 0 or n > Sys.max_string_length .

       Since 4.02.0

       val copy : string -> string

       Deprecated.  Because strings are immutable, it doesn't make much sense to  make  identical
       copies of them.

       Return a copy of the given string.

       val sub : string -> int -> 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 .

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

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

       Deprecated.  This is a deprecated alias of Bytes.fill .

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

       Raise Invalid_argument if start and len do not designate a valid range of s .

       val blit : string -> int -> bytes -> int -> int -> unit

       Same as Bytes.blit_string .

       val concat : string -> string list -> string

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

       Raise Invalid_argument if the result is longer than Sys.max_string_length bytes.

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

       String.map f s applies function f in turn to all the characters of s (in increasing  index
       order) and stores the results in a new string that is returned.

       Since 4.00.0

       val mapi : (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 neither
       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.  All characters outside  the  ASCII  printable
       range (32..126) are escaped, as well as backslash and double-quote.

       If  there is no special character in the argument that needs escaping, return the original
       string itself, not a copy.

       Raise Invalid_argument if the result is longer than Sys.max_string_length bytes.

       The function Scanf.unescaped is a left inverse of escaped , i.e.  Scanf.unescaped (escaped
       s) = s for any string s (unless escape s fails).

       val index : string -> char -> int

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

       Raise 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 .

       Raise 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 .

       Raise Invalid_argument if i is not a valid position in s .  Raise 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   .    Raise
       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 .

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

       Raise 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 .

       Raise 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 .

       Raise Invalid_argument if stop < 0 or stop+1 is not a valid position in s .

       val uppercase : string -> string

       Deprecated.  Functions operating on Latin-1 character set are deprecated.

       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

       Deprecated.  Functions operating on Latin-1 character set are deprecated.

       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

       Deprecated.  Functions operating on Latin-1 character set are deprecated.

       Return a copy of the argument, with the first character set to uppercase,  using  the  ISO
       Latin-1 (8859-1) character set..

       val uncapitalize : string -> string

       Deprecated.  Functions operating on Latin-1 character set are deprecated.

       Return  a  copy  of the argument, with the first character set to lowercase, using the ISO
       Latin-1 (8859-1) character set..

       val uppercase_ascii : string -> string

       Return a copy of the argument, with all lowercase letters translated to  uppercase,  using
       the US-ASCII character set.

       Since 4.03.0

       val lowercase_ascii : string -> string

       Return  a  copy of the argument, with all uppercase letters translated to lowercase, using
       the US-ASCII character set.

       Since 4.03.0

       val capitalize_ascii : string -> string

       Return a copy of the argument, with the  first  character  set  to  uppercase,  using  the
       US-ASCII character set.

       Since 4.03.0

       val uncapitalize_ascii : string -> string

       Return  a  copy  of  the  argument,  with  the first character set to lowercase, using the
       US-ASCII character set.

       Since 4.03.0

       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 .

       val equal : t -> t -> bool

       The equal function for strings.

       Since 4.03.0

       val split_on_char : char -> string -> string list

       String.split_on_char sep s returns the list of all (possibly empty) substrings of  s  that
       are delimited by the sep character.

       The function's output is specified by the following invariants:

       -The list is not empty.

       -Concatenating its elements using sep as a separator returns a string equal to the input (
       String.concat (String.make 1 sep) (String.split_on_char sep s) = s ).

       -No string in the result contains the sep character.

       Since 4.04.0

   Iterators
       val to_seq : t -> char Seq.t

       Iterate on the string, in increasing index  order.  Modifications  of  the  string  during
       iteration will be reflected in the iterator.

       Since 4.07

       val to_seqi : t -> (int * char) Seq.t

       Iterate on the string, in increasing order, yielding indices along chars

       Since 4.07

       val of_seq : char Seq.t -> t

       Create a string from the generator

       Since 4.07