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ListLabels(3)			 OCaml library			 ListLabels(3)

NAME
       ListLabels - List operations.

Module
       Module	ListLabels

Documentation
       Module ListLabels
	: sig end

       List operations.

       Some  functions	are  flagged  as not tail-recursive.  A	tail-recursive
       function	uses constant stack space, while a non-tail-recursive function
       uses stack space	proportional to	the length of its list argument, which
       can be a	problem	with very long lists.  When the	function takes several
       list  arguments,	an approximate formula giving stack usage (in some un-
       specified constant unit)	is shown in parentheses.

       The above considerations	can usually be ignored if your lists  are  not
       longer than about 10000 elements.

       val length : 'a list -> int

       Return the length (number of elements) of the given list.

       val hd :	'a list	-> 'a

       Return  the  first  element  of the given list. Raise Failure hd	if the
       list is empty.

       val tl :	'a list	-> 'a list

       Return the given	list without its first element.	Raise  Failure	tl  if
       the list	is empty.

       val nth : 'a list -> int	-> 'a

       Return the n -th	element	of the given list.  The	first element (head of
       the list) is at position	0.  Raise Failure  nth	if  the	 list  is  too
       short.  Raise Invalid_argument List.nth if n is negative.

       val rev : 'a list -> 'a list

       List reversal.

       val append : 'a list -> 'a list -> 'a list

       Catenate	 two  lists.   Same  function  as  the infix operator @	.  Not
       tail-recursive (length of the first argument).  The @ operator  is  not
       tail-recursive either.

       val rev_append :	'a list	-> 'a list -> 'a list

       ListLabels.rev_append  l1  l2  reverses	l1 and concatenates it to l2 .
       This is equivalent to ListLabels.rev  l1	 @  l2	,  but	rev_append  is
       tail-recursive and more efficient.

       val concat : 'a list list -> 'a list

       Concatenate a list of lists.  The elements of the argument are all con-
       catenated together (in  the  same  order)  to  give  the	 result.   Not
       tail-recursive  (length	of  the	 argument  +  length  of  the  longest
       sub-list).

       val flatten : 'a	list list -> 'a	list

       Same as concat .	 Not tail-recursive (length of the argument  +	length
       of the longest sub-list).

       === Iterators ===

       val iter	: f:('a	-> unit) -> 'a list -> unit

       ListLabels.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 : f:(int -> 'a	-> unit) -> 'a list -> unit

       Same as ListLabels.iter , but the function is applied to	the  index  of
       the element as first argument (counting from 0),	and the	element	itself
       as second argument.

       Since 4.00.0

       val map : f:('a -> 'b) -> 'a list -> 'b list

       ListLabels.map f	[a1; ...; an] applies function f to a1,	..., an	,  and
       builds the list [f a1; ...; f an] with the results returned by f	.  Not
       tail-recursive.

       val mapi	: f:(int -> 'a -> 'b) -> 'a list -> 'b list

       Same as ListLabels.map ,	but the	function is applied to	the  index  of
       the element as first argument (counting from 0),	and the	element	itself
       as second argument.

       Since 4.00.0

       val rev_map : f:('a -> 'b) -> 'a	list ->	'b list

       ListLabels.rev_map f l gives the	same result as ListLabels.rev (	 List-
       Labels.map f l) , but is	tail-recursive and more	efficient.

       val fold_left : f:('a ->	'b -> 'a) -> init:'a ->	'b list	-> 'a

       ListLabels.fold_left  f	a [b1; ...; bn]	is f (... (f (f	a b1) b2) ...)
       bn .

       val fold_right :	f:('a -> 'b -> 'b) -> 'a list -> init:'b -> 'b

       ListLabels.fold_right f [a1; ...; an] b is f a1 (f a2  (...  (f	an  b)
       ...))  .	 Not tail-recursive.

       === Iterators on	two lists ===

       val iter2 : f:('a -> 'b -> unit)	-> 'a list -> 'b list -> unit

       ListLabels.iter2	 f  [a1; ...; an] [b1; ...; bn]	calls in turn f	a1 b1;
       ...; f an bn .  Raise Invalid_argument if the two lists have  different
       lengths.

       val map2	: f:('a	-> 'b -> 'c) ->	'a list	-> 'b list -> 'c list

       ListLabels.map2	f  [a1;	 ...; an] [b1; ...; bn]	is [f a1 b1; ...; f an
       bn] .  Raise Invalid_argument if	the two	lists have different  lengths.
       Not tail-recursive.

       val rev_map2 : f:('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list

       ListLabels.rev_map2  f  l1 l2 gives the same result as ListLabels.rev (
       ListLabels.map2 f l1 l2)	, but is tail-recursive	and more efficient.

       val fold_left2 :	f:('a -> 'b -> 'c -> 'a) -> init:'a -> 'b list	->  'c
       list -> 'a

       ListLabels.fold_left2 f a [b1; ...; bn] [c1; ...; cn] is	f (... (f (f a
       b1 c1) b2 c2) ...) bn cn	.  Raise Invalid_argument  if  the  two	 lists
       have different lengths.

       val  fold_right2	 :  f:('a  -> 'b -> 'c -> 'c) -> 'a list -> 'b list ->
       init:'c -> 'c

       ListLabels.fold_right2 f	[a1; ...; an] [b1; ...;	bn] c is f a1 b1 (f a2
       b2  (...	 (f an bn c) ...))  .  Raise Invalid_argument if the two lists
       have different lengths.	Not tail-recursive.

       === List	scanning ===

       val for_all : f:('a -> bool) -> 'a list -> bool

       for_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 : f:('a -> bool) -> 'a list -> bool

       exists  p [a1; ...; an] checks if at least one element of the list sat-
       isfies the predicate p .	That is, it returns (p a1) || (p a2) ||	... ||
       (p an) .

       val for_all2 : f:('a -> 'b -> bool) -> 'a list -> 'b list -> bool

       Same  as	 ListLabels.for_all , but for a	two-argument predicate.	 Raise
       Invalid_argument	if the two lists have different	lengths.

       val exists2 : f:('a -> 'b -> bool) -> 'a	list ->	'b list	-> bool

       Same as ListLabels.exists , but for a  two-argument  predicate.	 Raise
       Invalid_argument	if the two lists have different	lengths.

       val mem : 'a -> set:'a list -> bool

       mem a l is true if and only if a	is equal to an element of l .

       val memq	: 'a ->	set:'a list -> bool

       Same  as	 ListLabels.mem	, but uses physical equality instead of	struc-
       tural equality to compare list elements.

       === List	searching ===

       val find	: f:('a	-> bool) -> 'a list -> 'a

       find p l	returns	the first element of the list  l  that	satisfies  the
       predicate p .  Raise Not_found if there is no value that	satisfies p in
       the list	l .

       val filter : f:('a -> bool) -> 'a list -> 'a list

       filter 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 pre-
       served.

       val find_all : f:('a -> bool) ->	'a list	-> 'a list

       find_all	is another name	for ListLabels.filter .

       val partition : f:('a ->	bool) -> 'a list -> 'a list * 'a list

       partition 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.

       === Association lists ===

       val assoc : 'a -> ('a * 'b) list	-> 'b

       assoc  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 .  Raise	Not_found if there is no value associ-
       ated with a in the list l .

       val assq	: 'a ->	('a * 'b) list -> 'b

       Same as ListLabels.assoc	, but uses physical equality instead of	struc-
       tural equality to compare keys.

       val mem_assoc : 'a -> map:('a * 'b) list	-> bool

       Same  as	ListLabels.assoc , but simply return true if a binding exists,
       and false if no bindings	exist for the given key.

       val mem_assq : 'a -> map:('a * 'b) list -> bool

       Same as ListLabels.mem_assoc , but uses physical	 equality  instead  of
       structural equality to compare keys.

       val remove_assoc	: 'a ->	('a * 'b) list -> ('a *	'b) list

       remove_assoc  a	l  returns  the	list of	pairs l	without	the first pair
       with key	a , if any.  Not tail-recursive.

       val remove_assq : 'a -> ('a * 'b) list -> ('a * 'b) list

       Same as ListLabels.remove_assoc , but uses physical equality instead of
       structural equality to compare keys.  Not tail-recursive.

       === Lists of pairs ===

       val split : ('a * 'b) list -> 'a	list * 'b list

       Transform  a  list  of pairs into a pair	of lists: split	[(a1,b1); ...;
       (an,bn)]	is ([a1; ...; an], [b1;	...; bn]) .  Not tail-recursive.

       val combine : 'a	list ->	'b list	-> ('a * 'b) list

       Transform a pair	of lists into a	list of	pairs: combine [a1;  ...;  an]
       [b1;  ...;  bn] is [(a1,b1); ...; (an,bn)] .  Raise Invalid_argument if
       the two lists have different lengths.  Not tail-recursive.

       === Sorting ===

       val sort	: cmp:('a -> 'a	-> int)	-> 'a list -> 'a list

       Sort a list in increasing order according  to  a	 comparison  function.
       The  comparison	function  must	return	0  if its arguments compare as
       equal, a	positive integer if the	first is greater, and a	negative inte-
       ger  if	the first is smaller (see Array.sort for a complete specifica-
       tion).  For example, Pervasives.compare is a suitable comparison	 func-
       tion.   The  resulting  list  is	 sorted	 in increasing order.  ListLa-
       bels.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 : cmp:('a -> 'a -> int) -> 'a list -> 'a	list

       Same as ListLabels.sort , but the sorting algorithm is guaranteed to be
       stable (i.e. elements that compare equal	are kept in their original or-
       der) .

       The current implementation uses Merge Sort. It runs  in	constant  heap
       space and logarithmic stack space.

       val fast_sort : cmp:('a -> 'a ->	int) ->	'a list	-> 'a list

       Same as ListLabels.sort or ListLabels.stable_sort , whichever is	faster
       on typical input.

       val merge : cmp:('a -> 'a -> int) -> 'a list -> 'a list -> 'a list

       Merge two lists:	Assuming that l1 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  com-
       pare equal, the elements	of l1 will be before the elements of l2	.  Not
       tail-recursive (sum of the lengths of the arguments).

OCamldoc			  2017-04-30			 ListLabels(3)

NAME | Module | Documentation

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