module String:sig..end
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 -> intval get : string -> int -> charString.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 -> unitString.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 -> bytesString.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 -> stringString.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) -> stringString.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.
val copy : string -> stringval sub : string -> int -> int -> stringString.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 -> unitString.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 -> unitBytes.blit_string.val concat : string -> string list -> stringString.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 -> unitString.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 -> unitString.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.val map : (char -> char) -> string -> stringString.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.val mapi : (int -> char -> char) -> string -> stringString.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.val 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.val escaped : string -> stringIf 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 -> intString.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 rindex : string -> char -> intString.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 index_from : string -> int -> char -> intString.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 rindex_from : string -> int -> char -> intString.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 contains : string -> char -> boolString.contains s c tests if character c
appears in the string s.val contains_from : string -> int -> char -> boolString.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 -> boolString.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 -> stringval lowercase : string -> stringval capitalize : string -> stringval uncapitalize : string -> stringval uppercase_ascii : string -> stringval lowercase_ascii : string -> stringval capitalize_ascii : string -> stringval uncapitalize_ascii : string -> stringtypet =string
val compare : t -> t -> intval equal : t -> t -> boolval split_on_char : char -> string -> string listString.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:
sep as a separator returns a
string equal to the input (String.concat (String.make 1 sep)
(String.split_on_char sep s) = s).sep character.