module String: sig .. endA 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.
let length: string => int;
let 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.
let set: (bytes, int, char) => unit;
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.
let create: int => bytes;
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.
let 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.
let 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
let copy: string => string;
let 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.
let fill: (bytes, int, int, char) => unit;
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.
let blit: (string, int, bytes, int, int) => unit;
Bytes.blit_string.let concat: (string, list(string)) => 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.
let 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]; ().let iteri: ((int, char) => unit, string) => unit;
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.let 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.let 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.let trim: string => string;
' ',
'\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.let escaped: string => string;
Raise Invalid_argument if the result is longer than
Sys.max_string_length bytes.
let 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.
let 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.
let 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.
let 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.
let contains: (string, char) => bool;
String.contains s c tests if character c
appears in the string s.let 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.
let 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.
let uppercase: string => string;
let lowercase: string => string;
let capitalize: string => string;
let uncapitalize: string => string;
type t = string;
let compare: (t, t) => int;
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.