Module BatText

module BatText: sig .. end
Heavyweight strings ("ropes")

This module implements ropes as described in Boehm, H., Atkinson, R., and Plass, M. 1995. Ropes: an alternative to strings. Softw. Pract. Exper. 25, 12 (Dec. 1995), 1315-1330.

Ropes are an alternative to strings which support efficient operations:

Functional nature and persistence

All operations are non-destructive: the original rope is never modified. When a new rope is returned as the result of an operation, it will share as much data as possible with its "parent". For instance, if a rope of length n undergoes m operations (assume n >> m) like set, append or prepend, the modified rope will only require O(m) space in addition to that taken by the original one.

However, Rope is an amortized data structure, and its use in a persistent setting can easily degrade its amortized time bounds. It is thus mainly intended to be used ephemerally. In some cases, it is possible to use Rope persistently with the same amortized bounds by explicitly rebalancing ropes to be reused using balance. Special care must be taken to avoid calling balance too frequently; in the limit, calling balance after each modification would defeat the purpose of amortization.

Limitations

The length of ropes is limited to approximately 700 Mb on 32-bit architectures, 220 Gb on 64 bit architectures.
Author(s): Mauricio Fernandez, Yoriyuki Yamagata, The Batteries Included Team


type t 
The type of the rope.
exception Out_of_bounds
Raised when an operation violates the bounds of the rope.
val max_length : int
Maximum length of the rope (number of UTF-8 characters).

Creation and conversions

val empty : t
The empty rope.
val of_latin1 : string -> t
Constructs a unicode rope from a latin-1 string.
val of_string : string -> t
of_string s returns a rope corresponding to the UTF-8 encoded string s.
val to_string : t -> string
to_string t returns a UTF-8 encoded string representing t
val of_uchar : BatUChar.t -> t
of_uchar c returns a rope containing exactly character c.
val of_char : char -> t
of_char c returns a rope containing exactly Latin-1 character c.
val make : int -> BatUChar.t -> t
make i c returns a rope of length i consisting of c chars; it is similar to String.make
val join : t -> t list -> t
Same as BatText.concat
val explode : t -> BatUChar.t list
explode s returns the list of characters in the rope s.
val implode : BatUChar.t list -> t
implode cs returns a rope resulting from concatenating the characters in the list cs.

Properties

val is_empty : t -> bool
Returns whether the rope is empty or not.
val length : t -> int
Returns the length of the rope (O(1)). This is number of UTF-8 characters.
val height : t -> int
Returns the height (depth) of the rope.
val balance : t -> t
balance r returns a balanced copy of the r rope. Note that ropes are automatically rebalanced when their height exceeds a given threshold, but balance allows to invoke that operation explicity.

Operations

val append : t -> t -> t
append r u concatenates the r and u ropes. In general, it operates in O(log(min n1 n2)) amortized time. Small ropes are treated specially and can be appended/prepended in amortized O(1) time.
val (^^^) : t -> t -> t
As BatText.append
val append_char : BatUChar.t -> t -> t
append_char c r returns a new rope with the c character at the end in amortized O(1) time.
val prepend_char : BatUChar.t -> t -> t
prepend_char c r returns a new rope with the c character at the beginning in amortized O(1) time.
val get : t -> int -> BatUChar.t
get r n returns the (n+1)th character from the rope r; i.e. get r 0 returns the first character. Operates in worst-case O(log size) time.
Raises Out_of_bounds if a character out of bounds is requested.
val set : t -> int -> BatUChar.t -> t
set r n c returns a copy of rope r where the (n+1)th character has been set to c. See also BatText.get. Operates in worst-case O(log size) time.
val sub : t -> int -> int -> t
sub r m n returns a sub-rope of r containing all characters whose indexes range from m to m + n - 1 (included). Operates in worst-case O(log size) time.
Raises Out_of_bounds in the same cases as sub.
val insert : int -> t -> t -> t
insert n r u returns a copy of the u rope where r has been inserted between the characters with index n and n + 1 in the original rope. The length of the new rope is length u + length r. Operates in amortized O(log(size r) + log(size u)) time.
val remove : int -> int -> t -> t
remove m n r returns the rope resulting from deleting the characters with indexes ranging from m to m + n - 1 (included) from the original rope r. The length of the new rope is length r - n. Operates in amortized O(log(size r)) time.
val concat : t -> t list -> t
concat sep sl concatenates the list of ropes sl, inserting the separator rope sep between each.

Iteration

val iter : (BatUChar.t -> unit) -> t -> unit
iter f r applies f to all the characters in the r rope, in order.
val iteri : ?base:int -> (int -> BatUChar.t -> unit) -> t -> unit
Operates like iter, but also passes the index of the character to the given function.
val range_iter : (BatUChar.t -> unit) -> int -> int -> t -> unit
rangeiter f m n r applies f to all the characters whose indices k satisfy m <= k < m + n. It is thus equivalent to iter f (sub m n r), but does not create an intermediary rope. rangeiter operates in worst-case O(n + log m) time, which improves on the O(n log m) bound from an explicit loop using get.
Raises Out_of_bounds in the same cases as sub.
val range_iteri : (int -> BatUChar.t -> unit) -> ?base:int -> int -> int -> t -> unit
As range_iter, but passes base + index of the character in the subrope defined by next to arguments.
val fold : ('a -> BatUChar.t -> 'a) -> 'a -> t -> 'a
Rope.fold f a r computes  f (... (f (f a r0) r1)...) rN-1  where rn = Rope.get n r  and N = length r.
val init : int -> (int -> BatUChar.t) -> t
init l f returns the rope of length l with the chars f 0 , f 1 , f 2 ... f (l-1).
val map : (BatUChar.t -> BatUChar.t) -> t -> t
map f s returns a rope where all characters c in s have been replaced by f c. *
val filter_map : (BatUChar.t -> BatUChar.t option) -> t -> t
filter_map f l calls (f a0) (f a1).... (f an) where a0..an are the characters of l. It returns the list of elements bi such as f ai = Some bi (when f returns None, the corresponding element of l is discarded).
val filter : (BatUChar.t -> bool) -> t -> t
filter f s returns a copy of rope s in which only characters c such that f c = true remain.
val enum : t -> BatUChar.t BatEnum.t
enumerate the rope's characters
Since 2.2.0
val backwards : t -> BatUChar.t BatEnum.t
enumerates the rope's characters, in reverse order
Since 2.2.0
val of_enum : BatUChar.t BatEnum.t -> t
converts the enumeration into a rope
Since 2.2.0

Finding

val index : t -> BatUChar.t -> int
index s c returns the position of the leftmost occurrence of character c in rope s.
Raises Not_found if c does not occur in s.
val index_from : t -> int -> BatUChar.t -> int
index_from r i c returns the character number of the first occurrence of character c in rope r after position i. index s c is equivalent to index_from s 0 c.
Raises
val rindex : t -> BatUChar.t -> int
Rope.rindex s c returns the position of the rightmost occurrence of character c in rope s.
Raises Not_found if c does not occur in s.
val rindex_from : t -> int -> BatUChar.t -> int
Same as BatText.rindex, but start searching at the character position given as second argument. rindex s c is equivalent to rindex_from s (length s - 1) c.
val contains : t -> BatUChar.t -> bool
contains s c tests if character c appears in the rope s.
val contains_from : t -> int -> BatUChar.t -> bool
contains_from s start c tests if character c appears in the subrope of s starting from start to the end of s.
Raises Invalid_argument if start is not a valid index of s.
val rcontains_from : t -> int -> BatUChar.t -> bool
rcontains_from s stop c tests if character c appears in the subrope of s starting from the beginning of s to index stop.
Raises Invalid_argument if stop is not a valid index of s.
val find : t -> t -> int
find s x returns the starting index of the first occurrence of rope x within rope s.

Note This implementation is optimized for short ropes.
Raises Not_found if x is not a subrope of s.

val find_from : t -> int -> t -> int
find_from s ofs x behaves as find s x but starts searching at offset ofs. find s x is equivalent to find_from s 0 x.
Raises
val rfind : t -> t -> int
rfind s x returns the starting index of the last occurrence of rope x within rope s.

Note This implementation is optimized for short ropes.
Raises Not_found if x is not a subrope of s.

val rfind_from : t -> int -> t -> int
rfind_from s ofs x behaves as rfind s x but starts searching at offset ofs. rfind s x is equivalent to rfind_from s (length s - 1) x.
Raises
val starts_with : t -> t -> bool
starts_with s x returns true if s is starting with x, false otherwise.
val ends_with : t -> t -> bool
ends_with s x returns true if the rope s is ending with x, false otherwise.
val exists : t -> t -> bool
exists str sub returns true if sub is a subrope of str or false otherwise.
val left : t -> int -> t
left r len returns the rope containing the len first characters of r
val right : t -> int -> t
left r len returns the rope containing the len last characters of r
val head : t -> int -> t
as BatText.left
val tail : t -> int -> t
tail r pos returns the rope containing all but the pos first characters of r
val strip : ?chars:BatUChar.t list -> t -> t
Returns the rope without the chars if they are at the beginning or at the end of the rope. By default chars are " \t\r\n".
val lchop : t -> t
Returns the same rope but without the first character. does nothing if the rope is empty.
val rchop : t -> t
Returns the same rope but without the last character. does nothing if the rope is empty.
val slice : ?first:int -> ?last:int -> t -> t
slice ?first ?last s returns a "slice" of the rope which corresponds to the characters s.[first], s.[first+1], ..., s[last-1]. Note that the character at index last is not included! If first is omitted it defaults to the start of the rope, i.e. index 0, and if last is omitted is defaults to point just past the end of s, i.e. length s. Thus, slice s is equivalent to copy s.

Negative indexes are interpreted as counting from the end of the rope. For example, slice ~last:-2 s will return the rope s, but without the last two characters.

This function never raises any exceptions. If the indexes are out of bounds they are automatically clipped.

val splice : t -> int -> int -> t -> t
splice s off len rep returns the rope in which the section of s indicated by off and len has been cut and replaced by rep.

Negative indices are interpreted as counting from the end of the string.

val fill : t -> int -> int -> BatUChar.t -> t
fill s start len c returns the rope in which characters number start to start + len - 1 of s has been replaced by c.
Raises Invalid_argument if start and len do not designate a valid subrope of s.
val blit : t -> int -> t -> int -> int -> t
blit src srcoff dst dstoff len returns a copy of dst in which len characters have been copied from rope src, starting at character number srcoff, to rope dst, starting at character number dstoff. It works correctly even if src and dst are the same rope, and the source and destination chunks overlap.
Raises Invalid_argument if srcoff and len do not designate a valid subrope of src, or if dstoff and len do not designate a valid subrope of dst.
val concat : t -> t list -> t
concat sep sl concatenates the list of ropes sl, inserting the separator rope sep between each.
val replace : str:t -> sub:t -> by:t -> bool * t
replace ~str ~sub ~by returns a tuple constisting of a boolean and a rope where the first occurrence of the rope sub within str has been replaced by the rope by. The boolean is true if a substitution has taken place, false otherwise.

Splitting around

val split : t -> t -> t * t
split s sep splits the rope s between the first occurrence of sep.
Raises Not_found if the separator is not found.
val rsplit : t -> t -> t * t
rsplit s sep splits the rope s between the last occurrence of sep.
Raises Not_found if the separator is not found.
val nsplit : t -> t -> t list
nsplit s sep splits the rope s into a list of ropes which are separated by sep. nsplit "" _ returns the empty list. If the separator is not found, it returns a list of the rope s. If two occurences of the separator are consecutive (with nothing in between), the empty rope is added in the sequence. For example, nsplit "a//b/" "/" is "a""""b""".
Raises Invalid_argument if the separator is empty
val compare : t -> t -> int
The comparison function for ropes, with the same specification as Pervasives.compare. Along with the type t, this function compare allows the module Rope to be passed as argument to the functors Set.Make and Map.Make.
val equal : t -> t -> bool
Equality of ropes (based on compare)
Since 2.2.0
val print : (t, 'a) BatIO.printer
Prints a rope to the given out_channel
val read_char : BatIO.input -> BatUChar.t
Read one Unicode char from a UTF-8 encoded input
val read_text : BatIO.input -> int -> t
Read up to n chars from a UTF-8 encoded input
val read_line : BatIO.input -> t
Read a line of UTF-8
val read_all : BatIO.input -> t
Read the whole contents of a UTF-8 encoded input
val write_char : (BatUChar.t, 'a) BatIO.printer
Write one uchar to a UTF-8 encoded output.
val write_text : (t, 'a) BatIO.printer
Write a character text onto a UTF-8 encoded output.
val write_line : (t, 'a) BatIO.printer
Write one line onto a UTF-8 encoded output, followed by a \n.
val lines_of : BatIO.input -> t BatEnum.t
offer the lines of a UTF-8 encoded input as an enumeration
val chars_of : BatIO.input -> BatUChar.t BatEnum.t
offer the characters of an UTF-8 encoded input as an enumeration
val output_text : unit BatIO.output -> t -> unit
Write the text on the given output channel.