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 .

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

       All new code should avoid this feature and be compiled with the -safe-string  command-line
       option to enforce the separation between the types string and bytes .

       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 Pervasives.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