include module type of String
Strings
val make : int -> char -> stringmake n c is a string of length n with each index holding the character c.
val init : int -> (int -> char) -> stringinit n f is a string of length n with index i holding the character f i (called in increasing index order).
val length : string -> intlength s is the length (number of bytes/characters) of s.
val get : string -> int -> charget s i is the character at index i in s. This is the same as writing s.[i].
val of_char : char -> stringof_char c is c as a string.
val of_bytes : bytes -> stringReturn a new string that contains the same bytes as the given byte sequence.
val to_bytes : string -> bytesReturn a new byte sequence that contains the same bytes as the given string.
val blit : string -> int -> bytes -> int -> int -> unitConcatenating
Note. The Stdlib.(^) binary operator concatenates two strings.
val concat : string -> string list -> stringconcat sep ss concatenates the list of strings ss, inserting the separator string sep between each.
val cat : string -> string -> stringcat s1 s2 concatenates s1 and s2 (s1 ^ s2).
Predicates and comparisons
val equal : t -> t -> boolequal s0 s1 is true if and only if s0 and s1 are character-wise equal.
val compare : t -> t -> intcompare s0 s1 sorts s0 and s1 in lexicographical order. compare behaves like Stdlib.compare on strings but may be more efficient.
val is_empty : string -> boolis_empty s is true if and only if s is an empty string.
val starts_with : prefix:string -> string -> boolstarts_with ~prefix s is true if and only if s starts with prefix.
val ends_with : suffix:string -> string -> boolends_with ~suffix s is true if and only if s ends with suffix.
val includes : affix:string -> string -> boolincludes affix s is true if and only if affix occurs in s.
Note. To test the same affix string multiple times, partially applying the ~affix argument and using the resulting function repeatedly is more efficient.
val contains_from : string -> int -> char -> boolcontains_from s start c is true if and only if c appears in s after position start.
val rcontains_from : string -> int -> char -> boolrcontains_from s stop c is true if and only if c appears in s before position stop+1.
val contains : string -> char -> boolval sub : string -> int -> int -> stringsub s pos len is a string of length len, containing the substring of s that starts at position pos and has length len.
Splitting strings
Splitting with magnitudes
val take_first : int -> string -> stringtake_first n s are the first n bytes of s. This is s if n >= length s and "" if n <= 0.
val take_last : int -> string -> stringtake_last n s are the last n bytes of s. This is s if n >= length s and "" if n <= 0.
val drop_first : int -> string -> stringdrop_first n s is s without the first n bytes of s. This is "" if n >= length s and s if n <= 0.
val drop_last : int -> string -> stringdrop_last n s is s without the last n bytes of s. This is "" if n >= length s and s if n <= 0.
val cut_first : int -> string -> string * stringcut_first n v is (take_first n v, drop_first n v).
val cut_last : int -> string -> string * stringcut_last n v is (drop_last n v, take_last n v).
Splitting with predicates
val take_first_while : (char -> bool) -> string -> stringtake_first_while p s is the first consecutive bytes of s satisfying the predicate p.
val take_last_while : (char -> bool) -> string -> stringtake_last_while p s is the last consecutive bytes of s satisfying the predicate p.
val drop_first_while : (char -> bool) -> string -> stringdrop_first_while p s is s without the first consecutive bytes of s satisfying the predicate p.
val drop_last_while : (char -> bool) -> string -> stringdrop_last_while p s is s without the last consecutive bytes of s satisfying the predicate p.
val cut_first_while : (char -> bool) -> string -> string * stringcut_first_while p s is (take_first_while p s, drop_first_while p s).
val cut_last_while : (char -> bool) -> string -> string * stringcut_last_while p s is (drop_last_while p s, take_last_while p s).
Splitting with separators
Note. To split the same sep string multiple times, partially applying the ~sep argument of these functions and using the resulting function repeatedly is more efficient.
val split_first : sep:string -> string -> (string * string) optionsplit_first sep s is the pair Some (left, right) made of the two (possibly empty) substrings of s that are delimited by the first match of the separator sep in s or None if sep can't be found. Search for sep starts at position 0 and uses find_first.
If sep is "", this is Some ("", s).
The invariant concat sep [left; right] = s holds.
val split_last : sep:string -> string -> (string * string) optionsplit_last sep s is the pair Some (left, right) made of the two (possibly empty) substrings of s that are delimited by the last match of the separator sep in s or None if sep can't be found. Search for sep starts at position length s and uses find_last.
If sep is "", this is Some (s, "").
The invariant concat sep [left; right] = s holds.
val split_all : sep:string -> ?drop:(string -> bool) -> string -> string listsplit_all sep s is the list of all substrings of s that are delimited by non-overlapping matches of the separator sep or the list [s] if sep can't be found. Search for sep starts at position 0 in increasing indexing order and uses find_all.
Substrings sub for which drop sub is true are not included in the result. drop defaults to Fun.const false.
If sep is "", this is [""; c0; ...; cn; ""] with ci the string of_char s.[i].
The invariant concat sep (split_all sep s) = s holds.
val rsplit_all : sep:string -> ?drop:(string -> bool) -> string -> string listrsplit_all sep s is the list of all substrings of s that are delimited by non-overlapping matches of the separator sep or [s] if sep can't be found. Search for sep starts at position length s in decreasing indexing order and uses rfind_all.
Substrings sub for which drop sub is true are not included in the result. drop defaults to Fun.const false.
If sep is "", this is [""; c0; ...; cn; ""] with ci the string of_char s.[i].
The invariant concat sep (rsplit_all sep s) = s holds.
val split_on_char : char -> string -> string listsplit_on_char sep s is the list of all (possibly empty) substrings of s that are delimited by the character sep. If s is empty, the result is the singleton list [""].
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.
val map : (char -> char) -> string -> stringmap f s is the string resulting from applying f to all the characters of s in increasing order.
val mapi : (int -> char -> char) -> string -> stringmapi f s is like map but the index of the character is also passed to f.
val fold_left : ('acc -> char -> 'acc) -> 'acc -> string -> 'accfold_left f x s computes f (... (f (f x s.[0]) s.[1]) ...) s.[n-1], where n is the length of the string s.
val fold_right : (char -> 'acc -> 'acc) -> string -> 'acc -> 'accfold_right f s x computes f s.[0] (f s.[1] ( ... (f s.[n-1] x) ...)), where n is the length of the string s.
val exists : (char -> bool) -> string -> boolexists p s checks if at least one character of s satisfies the predicate p.
val trim : string -> stringtrim s is s without leading and trailing whitespace. Whitespace characters are: ' ', '\x0C' (form feed), '\n', '\r', and '\t'.
val escaped : string -> stringescaped 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 (0x5C) 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).
val uppercase_ascii : string -> stringuppercase_ascii s is s with all lowercase letters translated to uppercase, using the US-ASCII character set.
val lowercase_ascii : string -> stringlowercase_ascii s is s with all uppercase letters translated to lowercase, using the US-ASCII character set.
val capitalize_ascii : string -> stringcapitalize_ascii s is s with the first character set to uppercase, using the US-ASCII character set.
val uncapitalize_ascii : string -> stringuncapitalize_ascii s is s with the first character set to lowercase, using the US-ASCII character set.
Traversing
val iter : (char -> unit) -> string -> unititer 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 -> unititeri is like iter, but the function is also given the corresponding character index.
Finding indices
val find_first_index : (char -> bool) -> ?start:int -> string -> int optionfind_first_index p start s is the index of the first character of s that satisfies predicate p at or after the index or position start (defaults to 0).
If start is length s, the result is always None.
val find_last_index : (char -> bool) -> ?start:int -> string -> int optionfind_last_index p start s is the index of the last character of s that satisfies predicate p at or before the index or position start (defaults to length s).
val index_from : string -> int -> char -> intindex_from s i c is the index of the first occurrence of c in s after position i.
val index_from_opt : string -> int -> char -> int optionindex_from_opt s i c is the index of the first occurrence of c in s after position i (if any).
val rindex_from : string -> int -> char -> intrindex_from s i c is the index of the last occurrence of c in s before position i+1.
val rindex_from_opt : string -> int -> char -> int optionrindex_from_opt s i c is the index of the last occurrence of c in s before position i+1 (if any).
val index : string -> char -> intval index_opt : string -> char -> int optionval rindex : string -> char -> intval rindex_opt : string -> char -> int optionFinding substrings
Note. To find the same sub string multiple times, partially applying the ~sub argument of these functions and using the resulting function repeatedly is more efficient
val find_first : sub:string -> ?start:int -> string -> int optionfind_first sub start s is the starting position of the first occurrence of sub in s at or after the index or position start (defaults to 0).
If sub is "" the result is Some start. The result of the function is always a valid index of s except when sub is "" and start is length s.
val find_last : sub:string -> ?start:int -> string -> int optionfind_last sub start s is the starting position of the last occurrence of sub in s at or before the index or position start (defaults to String.length s).
If sub is "" the result is Some start. The result of the function is always a valid index of s except when sub is "" and start is length s.
val find_all :
sub:string ->
(int -> 'acc -> 'acc) ->
?start:int ->
string ->
'acc ->
'accfind_all sub f start s acc, starting with acc, folds f by increasing index order over all non-overlapping starting positions of sub in s at or after the index or position start (defaults to 0). The result is acc if sub could not be found in s.
If sub is "", f gets invoked on all positions of s at or after start.
val rfind_all :
sub:string ->
(int -> 'acc -> 'acc) ->
?start:int ->
string ->
'acc ->
'accrfind_all sub f start s acc, starting with acc, folds f by decreasing index order over all non-overlapping starting positions of sub in s at or before the index or position start (defaults to String.length s). The result is acc if sub could not be found in s.
If sub is "", f gets invoked on all positions of s at or before start.
Replacing substrings
Note. To replace the same sub string multiple times, partially applying the ~sub argument of these functions and using the resulting function repeatedly is more efficient.
val replace_first : sub:string -> by:string -> ?start:int -> string -> stringreplace_first sub by start s replaces by by the first occurrence of sub in s at or after the index or position start (defaults to 0).
If sub is "", this inserts by at position start.
val replace_last : sub:string -> by:string -> ?start:int -> string -> stringreplace_last sub by start s replaces by by the last occurrence of sub in s at or after the index or position start (defaults to String.length s).
If sub is "", this inserts by at position start.
val replace_all : sub:string -> by:string -> ?start:int -> string -> stringreplace_all sub by start s replaces by by all non-overlapping occurrences of sub in s at or after the index or position start (defaults to 0). Occurrences are found in increasing indexing order.
If sub is "", this inserts by on all positions from start on.
Strings and Sequences
to_seq s is a sequence made of the string's characters in increasing order.
val to_seqi : t -> (int * char) Seq.tto_seqi s is like to_seq but also tuples the corresponding index.
of_seq s is a string made of the sequence's characters.
UTF decoding and validations
UTF-8
get_utf_8_uchar b i decodes an UTF-8 character at index i in b.
val is_valid_utf_8 : t -> boolis_valid_utf_8 b is true if and only if b contains valid UTF-8 data.
UTF-16BE
get_utf_16be_uchar b i decodes an UTF-16BE character at index i in b.
val is_valid_utf_16be : t -> boolis_valid_utf_16be b is true if and only if b contains valid UTF-16BE data.
UTF-16LE
get_utf_16le_uchar b i decodes an UTF-16LE character at index i in b.
val is_valid_utf_16le : t -> boolis_valid_utf_16le b is true if and only if b contains valid UTF-16LE data.
Spellchecking
val edit_distance : ?limit:int -> t -> t -> intedit_distance s0 s1 is the number of single character edits (understood as insertion, deletion, substitution, transposition) that are needed to change s0 into s1.
If limit is provided the function returns with limit as soon as it was determined that s0 and s1 have distance of at least limit. This is faster if you have a fixed limit, for example for spellchecking.
The function assumes the strings are UTF-8 encoded and uses Uchar.t for the notion of character. Decoding errors are replaced by Uchar.rep. Normalizing the strings to NFC gives better results.
Note. This implements the simpler Optimal String Alignment (OSA) distance, not the Damerau-Levenshtein distance. With this function "ca" and "abc" have a distance of 3 not 2.
val spellcheck :
?max_dist:(string -> int) ->
((string -> unit) -> unit) ->
string ->
string listspellcheck iter_dict s are the strings enumerated by the iterator iter_dict whose edit distance to s is the smallest and at most max_dist s. If multiple corrections are returned their order is as found in iter_dict. The default max_dist s is:
0 if s has 0 to 2 Unicode characters.1 if s has 3 to 4 Unicode characters.2 otherwise.
If your dictionary is a list l, a suitable iter_dict is given by (fun yield -> List.iter yield l).
All strings are assumed to be UTF-8 encoded, decoding errors are replaced by Uchar.rep characters.
Binary decoding of integers
The functions in this section binary decode integers from strings.
All following functions raise Invalid_argument if the characters needed at index i to decode the integer are not available.
Little-endian (resp. big-endian) encoding means that least (resp. most) significant bytes are stored first. Big-endian is also known as network byte order. Native-endian encoding is either little-endian or big-endian depending on Sys.big_endian.
32-bit and 64-bit integers are represented by the int32 and int64 types, which can be interpreted either as signed or unsigned numbers.
8-bit and 16-bit integers are represented by the int type, which has more bits than the binary encoding. These extra bits are sign-extended (or zero-extended) for functions which decode 8-bit or 16-bit integers and represented them with int values.
val get_uint8 : string -> int -> intget_uint8 b i is b's unsigned 8-bit integer starting at character index i.
val get_int8 : string -> int -> intget_int8 b i is b's signed 8-bit integer starting at character index i.
val get_uint16_ne : string -> int -> intget_uint16_ne b i is b's native-endian unsigned 16-bit integer starting at character index i.
val get_uint16_be : string -> int -> intget_uint16_be b i is b's big-endian unsigned 16-bit integer starting at character index i.
val get_uint16_le : string -> int -> intget_uint16_le b i is b's little-endian unsigned 16-bit integer starting at character index i.
val get_int16_ne : string -> int -> intget_int16_ne b i is b's native-endian signed 16-bit integer starting at character index i.
val get_int16_be : string -> int -> intget_int16_be b i is b's big-endian signed 16-bit integer starting at character index i.
val get_int16_le : string -> int -> intget_int16_le b i is b's little-endian signed 16-bit integer starting at character index i.
val get_int32_ne : string -> int -> int32get_int32_ne b i is b's native-endian 32-bit integer starting at character index i.
An unseeded hash function for strings, with the same output value as Hashtbl.hash. This function allows this module to be passed as argument to the functor Hashtbl.Make.
val seeded_hash : int -> t -> intval get_int32_be : string -> int -> int32get_int32_be b i is b's big-endian 32-bit integer starting at character index i.
val get_int32_le : string -> int -> int32get_int32_le b i is b's little-endian 32-bit integer starting at character index i.
val get_int64_ne : string -> int -> int64get_int64_ne b i is b's native-endian 64-bit integer starting at character index i.
val get_int64_be : string -> int -> int64get_int64_be b i is b's big-endian 64-bit integer starting at character index i.
val get_int64_le : string -> int -> int64get_int64_le b i is b's little-endian 64-bit integer starting at character index i.