Module Stdlib.String

module String: String

Strings

type t = string

The type for strings.

val make : int -> char -> string

make n c is a string of length n with each index holding the character c.

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

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

init n f is a string of length n with index i holding the character f i (called in increasing index order).

Since 4.02.0
Raises Invalid_argument if n < 0 or n > Sys.max_string_length.

val length : string -> int

length s is the length (number of bytes/characters) of s.

val get : string -> int -> char

get s i is the character at index i in s. This is the same as writing s.[i].

Raises Invalid_argument if i not an index of s.

Concatenating

Note. The (^) binary operator concatenates two strings.

val concat : string -> string list -> string

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

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

Predicates and comparisons

val equal : t -> t -> bool

equal s0 s1 is true if and only if s0 and s1 are character-wise equal.

Since 4.03.0 (4.05.0 in StringLabels)

val compare : t -> t -> int

compare s0 s1 sorts s0 and s1 in lexicographical order. compare behaves like compare on strings but may be more efficient.

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

contains_from s start c is true if and only if c appears in s after position start.

Raises Invalid_argument if start is not a valid position in s.

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

rcontains_from s stop c is true if and only if c appears in s before position stop+1.

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

val contains : string -> char -> bool

contains s c is String.contains_from s 0 c.

Extracting substrings

val sub : string -> int -> int -> string

sub s pos len is a string of length len, containing the substring of s that starts at position pos and has length len.

Raises Invalid_argument if pos and len do not designate a valid substring of s.

val split_on_char : char -> string -> string list

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

The function's result 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 (concat (make 1 sep) (split_on_char sep s) = s).
No string in the result contains the sep character.

Since 4.04.0 (4.05.0 in StringLabels)

Transforming

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

map f s is the string resulting from applying f to all the characters of s in increasing order.

Since 4.00.0

val mapi : (int -> char -> char) -> string -> string

mapi f s is like String.map but the index of the character is also passed to f.

Since 4.02.0

val trim : string -> string

trim s is s without leading and trailing whitespace. Whitespace characters are: ' ', '\x0C' (form feed), '\n', '\r', and '\t'.

Since 4.00.0

val escaped : string -> string

escaped s is s with special characters represented by escape sequences, following the lexical conventions of OCaml.

All characters outside the US-ASCII printable range [0x20;0x7E] are escaped, as well as backslash (0x2F) and double-quote (0x22).

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

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

val uppercase_ascii : string -> string

uppercase_ascii s is s with all lowercase letters translated to uppercase, using the US-ASCII character set.

Since 4.03.0 (4.05.0 in StringLabels)

val lowercase_ascii : string -> string

lowercase_ascii s is s with all uppercase letters translated to lowercase, using the US-ASCII character set.

Since 4.03.0 (4.05.0 in StringLabels)

val capitalize_ascii : string -> string

capitalize_ascii s is s with the first character set to uppercase, using the US-ASCII character set.

Since 4.03.0 (4.05.0 in StringLabels)

val uncapitalize_ascii : string -> string

uncapitalize_ascii s is s with the first character set to lowercase, using the US-ASCII character set.

Since 4.03.0 (4.05.0 in StringLabels)

Traversing

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

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.[length s - 1]; ().

val iteri : (int -> char -> unit) -> string -> unit

iteri is like String.iter, but the function is also given the corresponding character index.

Since 4.00.0

Searching

val index_from : string -> int -> char -> int

index_from s i c is the index of the first occurrence of c in s after position i.

Raises
- Not_found if c does not occur in s after position i.
- Invalid_argument if i is not a valid position in s.

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

index_from_opt s i c is the index of the first occurrence of c in s after position i (if any).

Since 4.05
Raises Invalid_argument if i is not a valid position in s.

val rindex_from : string -> int -> char -> int

rindex_from s i c is the index of the last occurrence of c in s before position i+1.

Raises
- Not_found if c does not occur in s before position i+1.
- Invalid_argument if i+1 is not a valid position in s.

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

rindex_from_opt s i c is the index of the last occurrence of c in s before position i+1 (if any).

Since 4.05
Raises Invalid_argument if i+1 is not a valid position in s.

val index : string -> char -> int

index s c is String.index_from s 0 c.

val index_opt : string -> char -> int option

index_opt s c is String.index_from_opt s 0 c.

Since 4.05

val rindex : string -> char -> int

rindex s c is String.rindex_from s (length s - 1) c.

val rindex_opt : string -> char -> int option

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

Since 4.05

Converting

val to_seq : t -> char Seq.t

to_seq s is a sequence made of the string's characters in increasing order. In "unsafe-string" mode, modifications of the string during iteration will be reflected in the iterator.

Since 4.07

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

to_seqi s is like String.to_seq but also tuples the corresponding index.

Since 4.07

val of_seq : char Seq.t -> t

of_seq s is a string made of the sequence's characters.

Since 4.07

Deprecated functions

val create : int -> bytes

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

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.

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

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

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 set s n c.

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

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

blit src src_pos dst dst_pos len copies len bytes from the string src, starting at index src_pos, to byte sequence dst, starting at character number dst_pos.

Raises Invalid_argument if src_pos and len do not designate a valid range of src, or if dst_pos and len do not designate a valid range of dst.

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

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

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

Raises Invalid_argument if pos and len do not designate a valid substring of 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.