Provided by: ocaml-nox_4.02.3-5ubuntu2_amd64 #### 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
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

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  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 : 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 ( ListLabels.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 satisfies 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 structural 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 preserved.

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 associated with a in the list l .

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

Same as ListLabels.assoc , but uses physical equality instead of  structural  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 integer if the first is smaller (see Array.sort for a  complete
specification).   For  example, Pervasives.compare is a suitable comparison function.  The
resulting list is sorted in increasing order.  ListLabels.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 order) .

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