List(3) 							   OCaml library							   List(3)

NAME

       List - List operations.

Module
       Module	List

Documentation
       Module List
	: 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 unspecified 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

       List.rev_append	l1  l2	reverses l1 and concatenates it to l2 .  This is equivalent to List.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 concatenated 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 : ('a -> unit) -> 'a list -> unit

       List.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 -> unit

       Same  as List.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 : ('a -> 'b) -> 'a list -> 'b list

       List.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 : (int -> 'a -> 'b) -> 'a list -> 'b list

       Same  as  List.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.  Not tail-recursive.

       Since 4.00.0

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

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

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

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

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

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

       === Iterators on two lists ===

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

       List.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 : ('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list

       List.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 : ('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list

       List.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 -> 'a

       List.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 : ('a -> 'b -> 'c -> 'c) -> 'a list -> 'b list -> 'c -> 'c

       List.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 : ('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 : ('a -> bool) -> 'a list -> bool

       exists  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 -> bool

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

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

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

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

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

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

       Same as List.mem , but uses physical equality instead of structural equality to compare list elements.

       === List searching ===

       val find : ('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 : ('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 preserved.

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

       find_all is another name for List.filter .

       val partition : ('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 associated with a in the list l .

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

       Same as List.assoc , but uses physical equality instead of structural equality to compare keys.

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

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

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

       Same as List.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 List.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 : ('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 integer if the first is smaller (see Array.sort for a complete specifica-
       tion).  For example, Pervasives.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 list

       Same  as  List.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 list

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

       val merge : ('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 compare equal, the elements of l1 will be before the elements of l2 .  Not
       tail-recursive (sum of the lengths of the arguments).

OCamldoc							    2014-06-09								   List(3)