Module CCString

Basic String Utils

type 'a iter = ('a -> unit) -> unit

Fast internal iterator.

  • since 2.8
type 'a gen = unit -> 'a option
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 create : int -> bytes

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

Return a copy of the given string.

  • deprecated

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

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

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.

  • deprecated

    This is a deprecated alias of Bytes.fill.

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 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

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.

  • deprecated

    Functions operating on Latin-1 character set are deprecated.

val lowercase : string -> string

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.

  • deprecated

    Functions operating on Latin-1 character set are deprecated.

val capitalize : string -> string

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

  • deprecated

    Functions operating on Latin-1 character set are deprecated.

val uncapitalize : string -> string

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

  • deprecated

    Functions operating on Latin-1 character set are deprecated.

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 equal : t -> t -> bool

The equal function for strings.

  • since 4.03.0

Iterators

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

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

  • since 4.07
val length : t -> int

length s returns the length (number of characters) of the given string s.

val blit : t -> int -> Bytes.t -> int -> int -> unit

blit src src_pos dst dst_pos len copies len characters from string src starting at character indice src_pos, to the Bytes sequence dst starting at character indice dst_pos. Like String.blit. Compatible with the -safe-string option.

val fold : ('a -> char -> 'a) -> 'a -> t -> 'a

fold f init s folds on chars by increasing index. Computes f(… (f (f init s.[0]) s.[1]) …) s.[n-1].

  • since 0.7
val foldi : ('a -> int -> char -> 'a) -> 'a -> t -> 'a

foldi f init s is just like fold, but it also passes in the index of each chars as second argument to the folded function f.

  • since 3.3

Conversions

val to_gen : t -> char gen

to_gen s returns the gen of characters contained in the string s.

val to_iter : t -> char iter

to_iter s returns the iter of characters contained in the string s.

  • since 2.8
val to_seq : t -> char Seq.t

to_seq s returns the Seq.t of characters contained in the string s. Renamed from to std_seq since 3.0.

  • since 3.0
val to_list : t -> char list

to_list s returns the list of characters contained in the string s.

val pp_buf : Buffer.t -> t -> unit

pp_buf buf s prints s to the buffer buf. Renamed from pp since 2.0.

val pp : Format.formatter -> t -> unit

pp f s prints the string s within quotes to the formatter f. Renamed from print since 2.0.

val compare : string -> string -> int

compare s1 s2 compares the strings s1 and s2 and returns an integer that indicates their relative position in the sort order.

val is_empty : string -> bool

is_empty s returns true iff s is empty (i.e. its length is 0).

  • since 1.5
val hash : string -> int

hash s returns the hash value of s.

val rev : string -> string

rev s returns the reverse of s.

  • since 0.17
val pad : ?side:[ `Left | `Right ] -> ?c:char -> int -> string -> string

pad ~side ~c n s ensures that the string s is at least n bytes long, and pads it on the side with c if it's not the case.

  • parameter side

    determines where padding occurs (default: `Left).

  • parameter c

    the char used to pad (default: ' ').

  • since 0.17
val of_char : char -> string

of_char 'a' is "a".

  • since 0.19
val of_gen : char gen -> string

of_gen gen converts a gen of characters to a string.

val of_iter : char iter -> string

of_iter iter converts an iter of characters to a string.

  • since 2.8
val of_seq : char Seq.t -> string

of_seq seq converts a seq of characters to a string. Renamed from of_std_seq since 3.0.

  • since 3.0
val of_list : char list -> string

of_list lc converts a list of characters lc to a string.

val of_array : char array -> string

of_array ac converts an array of characters ac to a string.

val to_array : string -> char array

to_array s returns the array of characters contained in the string s.

val find : ?start:int -> sub:string -> string -> int

find ~start ~sub s returns the starting index of the first occurrence of sub within s or -1.

  • parameter start

    starting position in s.

val find_all : ?start:int -> sub:string -> string -> int gen

find_all ~start ~sub s finds all occurrences of sub in s, even overlapping instances and returns them in a generator gen.

  • parameter start

    starting position in s.

  • since 0.17
val find_all_l : ?start:int -> sub:string -> string -> int list

find_all_l ~sub s finds all occurrences of sub in s and returns them in a list.

  • parameter start

    starting position in s.

  • since 0.17
val mem : ?start:int -> sub:string -> string -> bool

mem ~start ~sub s is true iff sub is a substring of s.

  • since 0.12
val rfind : sub:string -> string -> int

rfind ~sub s finds sub in string s from the right, returns its first index or -1. Should only be used with very small sub.

  • since 0.12
val replace : ?which:[ `Left | `Right | `All ] -> sub:string -> by:string -> string -> string

replace ~which ~sub ~by s replaces some occurrences of sub by by in s.

  • parameter which

    decides whether the occurrences to replace are:

    • `Left first occurrence from the left (beginning).
    • `Right first occurrence from the right (end).
    • `All all occurrences (default).
  • since 0.14
val is_sub : sub:string -> int -> string -> int -> sub_len:int -> bool

is_sub ~sub ~sub_pos s ~pos ~sub_len returns true iff the substring of sub starting at position sub_pos and of length sub_len is a substring of s starting at position pos.

val repeat : string -> int -> string

repeat s n creates a string by repeating the string s n times.

val prefix : pre:string -> string -> bool

prefix ~pre s returns true iff pre is a prefix of s.

val suffix : suf:string -> string -> bool

suffix ~suf s returns true iff suf is a suffix of s.

  • since 0.7
val chop_prefix : pre:string -> string -> string option

chop_prefix ~pre s removes pre from s if pre really is a prefix of s, returns None otherwise.

  • since 0.17
val chop_suffix : suf:string -> string -> string option

chop_suffix ~suf s removes suf from s if suf really is a suffix of s, returns None otherwise.

  • since 0.17
val take : int -> string -> string

take n s keeps only the n first chars of s.

  • since 0.17
val drop : int -> string -> string

drop n s removes the n first chars of s.

  • since 0.17
val take_drop : int -> string -> string * string

take_drop n s is take n s, drop n s.

  • since 0.17
val lines : string -> string list

lines s returns a list of the lines of s (splits along '\n').

  • since 0.10
val lines_gen : string -> string gen

lines_gen s returns the gen of the lines of s (splits along '\n').

  • since 0.10
val lines_iter : string -> string iter

lines_iter s returns the iter of the lines of s (splits along '\n').

  • since 3.2
val lines_seq : string -> string Seq.t

lines_seq s returns the Seq.t of the lines of s (splits along '\n').

  • since 3.2
val concat_gen : sep:string -> string gen -> string

concat_gen ~sep gen concatenates all strings of gen, separated with sep.

  • since 0.10
val concat_seq : sep:string -> string Seq.t -> string

concat_seq ~sep seq concatenates all strings of seq, separated with sep.

  • since 3.2
val concat_iter : sep:string -> string iter -> string

concat_iter ~sep iter concatenates all strings of iter, separated with sep.

  • since 3.2
val unlines : string list -> string

unlines ls concatenates all strings of ls, separated with '\n'.

  • since 0.10
val unlines_gen : string gen -> string

unlines_gen gen concatenates all strings of gen, separated with '\n'.

  • since 0.10
val unlines_iter : string iter -> string

unlines_iter iter concatenates all strings of iter, separated with '\n'.

  • since 3.2
val unlines_seq : string Seq.t -> string

unlines_seq seq concatenates all strings of seq, separated with '\n'.

  • since 3.2
val set : string -> int -> char -> string

set s i c creates a new string which is a copy of s, except for index i, which becomes c.

  • since 0.12
val iter : (char -> unit) -> string -> unit

iter f s applies function f on each character of s. Alias to String.iter.

  • since 0.12
val filter_map : (char -> char option) -> string -> string

filter_map f s calls (f a0) (f a1) … (f an) where a0 … an are the characters of s. It returns the string of characters ci such as f ai = Some ci (when f returns None, the corresponding element of s is discarded).

  • since 0.17
val filter : (char -> bool) -> string -> string

filter f s discards characters of s not satisfying f.

  • since 0.17
val uniq : (char -> char -> bool) -> string -> string

uniq eq s remove consecutive duplicate characters in s.

  • since 3.4
val flat_map : ?sep:string -> (char -> string) -> string -> string

flat_map ~sep f s maps each chars of s to a string, then concatenates them all.

  • parameter sep

    optional separator between each generated string.

  • since 0.12
val for_all : (char -> bool) -> string -> bool

for_all f s is true iff all characters of s satisfy the predicate f.

  • since 0.12
val exists : (char -> bool) -> string -> bool

exists f s is true iff some character of s satisfy the predicate f.

  • since 0.12
val drop_while : (char -> bool) -> t -> t

drop_while f s discards any characters of s starting from the left, up to the first character c not satisfying f c.

  • since 2.2
val rdrop_while : (char -> bool) -> t -> t

rdrop_while f s discards any characters of s starting from the right, up to the first character c not satisfying f c.

  • since 2.2
val ltrim : t -> t

ltrim s trims space on the left (see String.trim for more details).

  • since 1.2
val rtrim : t -> t

rtrim s trims space on the right (see String.trim for more details).

  • since 1.2

Operations on 2 strings

val map2 : (char -> char -> char) -> string -> string -> string

map2 f s1 s2 maps pairs of chars.

  • since 0.12
val iter2 : (char -> char -> unit) -> string -> string -> unit

iter2 f s1 s2 iterates on pairs of chars.

  • since 0.12
val iteri2 : (int -> char -> char -> unit) -> string -> string -> unit

iteri2 f s1 s2 iterates on pairs of chars with their index.

  • since 0.12
val fold2 : ('a -> char -> char -> 'a) -> 'a -> string -> string -> 'a

fold2 f init s1 s2 folds on pairs of chars.

  • since 0.12
val for_all2 : (char -> char -> bool) -> string -> string -> bool

for_all2 f s1 s2 returns true iff all pairs of chars satisfy the predicate f.

  • since 0.12
val exists2 : (char -> char -> bool) -> string -> string -> bool

exists2 f s1 s2 returns true iff a pair of chars satisfy the predicate f.

  • since 0.12

Ascii functions

Those functions are deprecated in String since 4.03, so we provide a stable alias for them even in older versions.

val equal_caseless : string -> string -> bool

equal_caseless s1 s2 compares s1 and s2 without respect to ascii lowercase.

  • since 1.2
val to_hex : string -> string

Convert a string with arbitrary content into a hexadecimal string.

  • since 3.8
val of_hex : string -> string option

Convert a string in hex into a string with arbitrary content.

  • since 3.8
val of_hex_exn : string -> string

Same as of_hex but fails harder.

  • since 3.8

Finding

A relatively efficient algorithm for finding sub-strings.

module Find : sig ... end

Splitting

module Split : sig ... end
val split_on_char : char -> string -> string list

split_on_char by s splits the string s along the given char by.

  • since 1.2
val split : by:string -> string -> string list

split ~by s splits the string s along the given string by. Alias to Split.list_cpy.

  • since 1.2

Utils

val compare_versions : string -> string -> int

compare_versions s1 s2 compares version strings s1 and s2, considering that numbers are above text.

  • since 0.13
val compare_natural : string -> string -> int

compare_natural s1 s2 is the Natural Sort Order, comparing chunks of digits as natural numbers. https://en.wikipedia.org/wiki/Natural_sort_order

  • since 1.3
val edit_distance : ?cutoff:int -> string -> string -> int

edit_distance ~cutoff s1 s2 is the edition distance between the two strings s1 and s2. This satisfies the classical distance axioms: it is always positive, symmetric, and satisfies the formula distance s1 s2 + distance s2 s3 >= distance s1 s3.

  • parameter cutoff

    if provided, it's a cap on the number of iterations. (since 3.0). This is useful if you just want to check whether the edit distance is less or equal than 2 without (use edit_distance s1 s2 ~cutoff:3 <= 2). note that contrary to what was previously documented here, the result can still be higher than cutoff if it's reached in <cutoff iterations. However if the result is < cutoff then it is accurate.

Infix operators

module Infix : sig ... end
include module type of Infix
val (=) : t -> t -> bool
  • since 3.0
val (<>) : t -> t -> bool
  • since 3.0
val (<) : t -> t -> bool
  • since 3.0
val (<=) : t -> t -> bool
  • since 3.0
val (>=) : t -> t -> bool
  • since 3.0
val (>) : t -> t -> bool
  • since 3.0