module BatList:sig..end
The OCaml standard library provides a module for list functions. This BatList module can be used to extend the List module or as a standalone module. It provides new functions and modify the behavior of some other ones (in particular all functions are now tail-recursive).
The following functions have the same behavior as the List
module ones but are tail-recursive: map, append, concat,
flatten, fold_right, remove_assoc, remove_assq,
split. That means they will not
cause a Stack_overflow when used on very long list.
The implementation might be a little more slow in bytecode, but compiling in native code will not affect performances.
This module extends Stdlib's
List
module, go there for documentation on the rest of the functions
and types.
type'at ='a list
include BatEnum.Enumerable
include BatInterfaces.Mappable
val is_empty : 'a list -> boolis_empty e returns true if e does not contains any element.val cons : 'a -> 'a list -> 'a listcons h t returns the list starting with h and continuing as tval first : 'a list -> 'aEmpty_list if
the list is empty (similar to hd).val hd : 'a list -> 'afirst, butFailure if the list is empty.val tl : 'a list -> 'a listFailure if the list is empty.val last : 'a list -> 'aEmpty_list if
the list is empty. This function takes linear time.val length : 'a list -> intval at : 'a list -> int -> 'aat l n returns the n-th element of the list l orInvalid_argument is the index is outside of l bounds. O(l)val rev : 'a list -> 'a listval append : 'a list -> 'a list -> 'a list@.
Tail-recursive O(length of the first argument).val rev_append : 'a list -> 'a list -> 'a listList.rev_append l1 l2 reverses l1 and concatenates it to l2.val concat : 'a list list -> 'a listval flatten : 'a list list -> 'a listconcat.val make : int -> 'a -> 'a listString.make, make n x returns a
list containing n elements x.val init : int -> (int -> 'a) -> 'a listArray.init, init n f returns the list containing
the results of (f 0),(f 1).... (f (n-1)).Invalid_argument if n < 0.val iter : ('a -> unit) -> 'a list -> unitList.iter f [a1; ...; an] applies function f in turn to
a1; ...; an. It is equivalent to
begin f a1; f a2; ...; f an; () end.val iteri : (int -> 'a -> unit) -> 'a list -> unititeri f l will call (f 0 a0);(f 1 a1) ... (f n an) where
a0..an are the elements of the list l.val map : ('a -> 'b) -> 'a list -> 'b listmap f [a0; a1; ...; an] applies function f to a0, a1, ..., an,
and builds the list [f a0; f a1; ...; f an]
with the results returned by f. Tail-recursive.val rev_map : ('a -> 'b) -> 'a list -> 'b listList.rev_map f l gives the same result as
List.rev (List.map f l).val mapi : (int -> 'a -> 'b) -> 'a list -> 'b listmapi f l will build the list containing
(f 0 a0);(f 1 a1) ... (f n an) where a0..an are the elements of
the list l.val fold_left : ('a -> 'b -> 'a) -> 'a -> 'b list -> 'aList.fold_left f a [b1; ...; bn] is
f (... (f (f a b1) b2) ...) bn.val fold_right : ('a -> 'b -> 'b) -> 'a list -> 'b -> 'bList.fold_right f [a0; a1; ...; an] b is
f a0 (f a1 (... (f an b) ...)). Tail-recursive.val reduce : ('a -> 'a -> 'a) -> 'a list -> 'aList.reduce f h::t is fold_left f h t.Empty_list on empty lists.val max : 'a list -> 'amax l returns the largest value in l as judged by
Pervasives.compareval min : 'a list -> 'amin l returns the smallest value in l as judged by
Pervasives.compareval sum : int list -> intsum l returns the sum of the integers of lval fsum : float list -> floatfsum l returns the sum of the floats of lval iter2 : ('a -> 'b -> unit) -> 'a list -> 'b list -> unitList.iter2 f [a0; a1; ...; an] [b0; b1; ...; bn] calls in turn
f a0 b0; f a1 b1; ...; f an bn.Different_list_size if the two lists have
different lengths.val map2 : ('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c listList.map2 f [a0; a1; ...; an] [b0; b1; ...; bn] is
[f a0 b0; f a1 b1; ...; f an bn].Different_list_size if the two lists have
different lengths. Tail-recursive.val rev_map2 : ('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c listList.rev_map2 f l1 l2 gives the same result as
List.rev (List.map2 f l1 l2), but is tail-recursive and
more efficient.val fold_left2 : ('a -> 'b -> 'c -> 'a) -> 'a -> 'b list -> 'c list -> 'aList.fold_left2 f a [b0; b1; ...; bn] [c0; c1; ...; cn] is
f (... (f (f a b0 c0) b1 c1) ...) bn cn.Different_list_size if the two lists have
different lengths.val fold_right2 : ('a -> 'b -> 'c -> 'c) -> 'a list -> 'b list -> 'c -> 'cList.fold_right2 f [a0; a1; ...; an] [b0; b1; ...; bn] c is
f a0 b0 (f a1 b1 (... (f an bn c) ...)).Different_list_size if the two lists have
different lengths. Tail-recursive.val mem : 'a -> 'a list -> boolmem a l is true if and only if a is equal
to an element of l.val memq : 'a -> 'a list -> boolList.mem, but uses physical equality instead of structural
equality to compare list elements.val for_all : ('a -> bool) -> 'a list -> boolfor_all p [a1; ...; an] checks if all elements of the list
satisfy the predicate p. That is, it returns
(p a1) && (p a2) && ... && (p an).val exists : ('a -> bool) -> 'a list -> boolexists p [a1; ...; an] checks if at least one element of
the list satisfies the predicate p. That is, it returns
(p a1) || (p a2) || ... || (p an).val for_all2 : ('a -> 'b -> bool) -> 'a list -> 'b list -> boolList.for_all, but for a two-argument predicate.Invalid_argument if the two lists have
different lengths.val exists2 : ('a -> 'b -> bool) -> 'a list -> 'b list -> boolList.exists, but for a two-argument predicate.Invalid_argument if the two lists have
different lengths.val find : ('a -> bool) -> 'a list -> 'afind p l returns the first element of the list l
that satisfies the predicate p.Not_found if there is no value that satisfies p in the
list l.val find_exn : ('a -> bool) -> exn -> 'a list -> 'afind_exn p e l returns the first element of l such as p x
returns true or raises e if such an element has not been found.val findi : (int -> 'a -> bool) -> 'a list -> int * 'afindi p e l returns the first element ai of l along with its
index i such that p i ai is true, orNot_found if no
such element has been found.val find_map : ('a -> 'b option) -> 'a list -> 'bfind_map pred list finds the first element of list for which
pred element returns Some r. It returns r immediately
once found orNot_found if no element matches the
predicate. See also BatList.filter_map.val rfind : ('a -> bool) -> 'a list -> 'arfind p l returns the last element x of l such as p x returns
true orNot_found if such element as not been found.val filter : ('a -> bool) -> 'a list -> 'a listfilter p l returns all the elements of the list l
that satisfy the predicate p. The order of the elements
in the input list is preserved.val filter_map : ('a -> 'b option) -> 'a list -> 'b listfilter_map f l calls (f a0) (f a1).... (f an) where a0,a1..an are
the elements 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 find_all : ('a -> bool) -> 'a list -> 'a listfind_all is another name for List.filter.val partition : ('a -> bool) -> 'a list -> 'a list * 'a listpartition p l returns a pair of lists (l1, l2), where
l1 is the list of all the elements of l that
satisfy the predicate p, and l2 is the list of all the
elements of l that do not satisfy p.
The order of the elements in the input list is preserved.val index_of : 'a -> 'a list -> int optionindex_of e l returns the index of the first occurrence of e
in l, or None if there is no occurrence of e in lval index_ofq : 'a -> 'a list -> int optionindex_ofq e l behaves as index_of e l except it uses
physical equalityval rindex_of : 'a -> 'a list -> int optionrindex_of e l returns the index of the last occurrence of e
in l, or None if there is no occurrence of e in lval rindex_ofq : 'a -> 'a list -> int optionrindex_ofq e l behaves as rindex_of e l except it uses
physical equalityval unique : ?eq:('a -> 'a -> bool) -> 'a list -> 'a listunique cmp l returns the list l without any duplicate element.
The default comparator ( = ) is used if no comparison function
specified.
Implementation Note: The current implementation removes any elements where the tail of the list contains an equal element, thus it keeps the *last* copy of each equal element.
This function takes O(n^2) time.
Since 2.0
See also sort_unique to save time in cases when reordering the list is
acceptable
val unique_cmp : ?cmp:('a -> 'a -> int) -> 'a list -> 'a listunique, except comparator parameter returns an int. Default
comparator is Pervasives.compare. This function takes O(n log n)
time.
Implementation Note: The current implementation removes subsequent
elements that compare as equal to earlier elements in the list,
thus it keeps the *first* copy of each equal element.
Since 1.3.0
val unique_hash : ?hash:('a -> int) -> ?eq:('a -> 'a -> bool) -> 'a list -> 'a listunique, except uses a hash table to cut down the expected
runtime to linear, assuming a good hash function. ?hash
defaults to Hashtbl.hash and ?eq defaults to (=).
Implementation Note: The current implementation removes subsequent
elements that hash and compare as equal to earlier elements in the
list, thus it keeps the *first* copy of each equal element.
Since 2.0.0
val assoc : 'a -> ('a * 'b) list -> 'bassoc a l returns the value associated with key a in the list of
pairs l. That is,
assoc a [ ...; (a,b); ...] = b
if (a,b) is the leftmost binding of a in list l.Not_found if there is no value associated with a in the
list l.val assoc_inv : 'b -> ('a * 'b) list -> 'aassoc_inv b l returns the key associated with value b in the list of
pairs l. That is, assoc b [ ...; (a,b); ...] = a
if (a,b) is the leftmost binding of a in list l.Not_found if there is no key associated with b in the
list l.val remove_assoc : 'a -> ('a * 'b) list -> ('a * 'b) listremove_assoc a l returns the list of
pairs l without the first pair with key a, if any.
Tail-recursive.val mem_assoc : 'a -> ('a * 'b) list -> boolList.assoc, but simply return true if a binding exists,
and false if no bindings exist for the given key.val assq : 'a -> ('a * 'b) list -> 'bList.assoc, but uses physical equality instead of structural
equality to compare keys.val assq_inv : 'b -> ('a * 'b) list -> 'aList.assoc_inv, but uses physical equality instead of structural
equality to compare keys.val remove_assq : 'a -> ('a * 'b) list -> ('a * 'b) listList.remove_assoc, but uses physical equality instead
of structural equality to compare keys. Tail-recursive.val mem_assq : 'a -> ('a * 'b) list -> boolList.mem_assoc, but uses physical equality instead of
structural equality to compare keys.val split_at : int -> 'a list -> 'a list * 'a listsplit_at n l returns two lists l1 and l2, l1 containing the
first n elements of l and l2 the others.Invalid_argument if
n is outside of l size bounds.val split_nth : int -> 'a list -> 'a list * 'a listsplit_at.val remove : 'a list -> 'a -> 'a listremove l x returns the list l without the first element x found
or returns l if no element is equal to x. Elements are compared
using ( = ).val remove_if : ('a -> bool) -> 'a list -> 'a listremove_if cmp l is similar to remove, but with cmp used
instead of ( = ).val remove_all : 'a list -> 'a -> 'a listremove_all l x is similar to remove but removes all elements that
are equal to x and not only the first one.val take : int -> 'a list -> 'a listtake n l returns up to the n first elements from list l, if
available.val drop : int -> 'a list -> 'a listdrop n l returns l without the first n elements, or the empty
list if l have less than n elements.val take_while : ('a -> bool) -> 'a list -> 'a listtake_while p xs returns the (possibly empty) longest prefix of
elements of xs that satisfy the predicate p.val drop_while : ('a -> bool) -> 'a list -> 'a listdrop_while p xs returns the suffix remaining after
takeWhile p xs.val interleave : ?first:'a -> ?last:'a -> 'a -> 'a list -> 'a listinterleave ~first ~last sep [a0;a1;a2;...;an] returns
first; a0; sep; a1; sep; a2; sep; ...; sep; an; last
Abstraction layer.
val enum : 'a list -> 'a BatEnum.tval of_enum : 'a BatEnum.t -> 'a listval backwards : 'a list -> 'a BatEnum.tval of_backwards : 'a BatEnum.t -> 'a listval split : ('a * 'b) list -> 'a list * 'b listsplit [(a0,b0); (a1,b1); ...; (an,bn)] is ([a0; a1; ...; an], [b0;
b1; ...; bn]).
Tail-recursive.val combine : 'a list -> 'b list -> ('a * 'b) listcombine [a0; a1; ...; an] [b0; b1; ...; bn] is
[(a0,b0); (a1,b1); ...; (an,bn)].Different_list_size if the two lists
have different lengths. Tail-recursive.val sort : ('a -> 'a -> int) -> 'a list -> 'a listPervasives.compare is a suitable comparison function.
The resulting list is sorted in increasing order.
List.sort is guaranteed to run in constant heap space
(in addition to the size of the result list) and logarithmic
stack space.
The current implementation uses Merge Sort. It runs in constant
heap space and logarithmic stack space.
val stable_sort : ('a -> 'a -> int) -> 'a list -> 'a listList.sort, but the sorting algorithm is guaranteed to
be stable (i.e. elements that compare equal are kept in their
original order) .
The current implementation uses Merge Sort. It runs in constant
heap space and logarithmic stack space.
val fast_sort : ('a -> 'a -> int) -> 'a list -> 'a listList.sort or List.stable_sort, whichever is faster
on typical input.val merge : ('a -> 'a -> int) -> 'a list -> 'a list -> 'a listl1 and l2 are sorted according to the
comparison function cmp, merge cmp l1 l2 will return a
sorted list containting all the elements of l1 and l2.
If several elements compare equal, the elements of l1 will be
before the elements of l2.
Not tail-recursive (sum of the lengths of the arguments).val sort_unique : ('a -> 'a -> int) -> 'a list -> 'a listsort_unique cmp l returns the list l sorted and without any duplicate
element. cmp is a usual comparison function providing total order.
This function takes O(n log n) time.
val group : ('a -> 'a -> int) -> 'a list -> 'a list listgroup cmp l returns list of groups and each group consists of
elements judged equal by comparison function cmp. Groups in the resulting
list appear in order given by cmp. All groups are always nonempty. group
returns [] only if l is empty.
For example group cmp [f;c;b;e;d;a] can give [[a;b];[c];[d;e;f]] if
following conditions are met:
cmp a b = 0, cmp b c = -1, cmp c d = -1, cmp d e = 0,...
val cartesian_product : 'a list -> 'b list -> ('a * 'b) listList.combine, this returns every pair
of elements formed out of the two lists.
cartesian_product [a0; a1; ...; an] [b0; b1; ...; bn] =
[(a0,b0);(a0,b1); ...; (a0,bn); (a1,b0); ..; (a1, bn);
...; (an,bn)]. The lists can be of unequal size.val n_cartesian_product : 'a list list -> 'a list list[a;b];[c];[d;e;f], returns
[a;c;d];[a;c;e];[a;c;f];[b;c;d];[b;c;e];[b;c;f], all
ways of choosing one element from each input list.val transpose : 'a list list -> 'a list listval print : ?first:string ->
?last:string ->
?sep:string ->
('a BatInnerIO.output -> 'b -> unit) ->
'a BatInnerIO.output -> 'b list -> unitval eq : 'a BatOrd.eq -> 'a list BatOrd.eqval ord : 'a BatOrd.ord -> 'a list BatOrd.ordval compare : 'a BatOrd.comp -> 'a list BatOrd.compmodule Eq:
module Ord:
module Comp:
val nth : 'a list -> int -> 'aat.val takewhile : ('a -> bool) -> 'a list -> 'a listBatList.take_whileval dropwhile : ('a -> bool) -> 'a list -> 'a listBatList.drop_whileList with functions
behaving slightly differently but having the same name. This is by
design:
the functions meant to override the corresponding functions of List.module Exceptionless:sig..end
module Infix:sig..end
module Labels:sig..end
List with labels.
val (@) : 'a list -> 'a list -> 'a listList.append.