module List: ListLabels;
type 'a t = 'a list =
| |
[] |
| |
(::) of 'a * 'a list |
An alias for the type of lists.
let length: list('a) => int;
Return the length (number of elements) of the given list.
let compare_lengths: (list('a), list('b)) => int;
Compare the lengths of two lists. compare_lengths l1 l2
is
equivalent to compare (length l1) (length l2)
, except that
the computation stops after reaching the end of the shortest list.
let compare_length_with: (list('a), ~len: int) => int;
Compare the length of a list to an integer. compare_length_with l len
is
equivalent to compare (length l) len
, except that the computation stops
after at most len
iterations on the list.
let cons: ('a, list('a)) => list('a);
cons x xs
is x :: xs
let hd: list('a) => 'a;
Return the first element of the given list.
Failure
if the list is empty.let tl: list('a) => list('a);
Return the given list without its first element.
Failure
if the list is empty.let nth: (list('a), int) => 'a;
Return the n
-th element of the given list.
The first element (head of the list) is at position 0.
Failure
if the list is too short.Invalid_argument
if n
is negative.let nth_opt: (list('a), int) => option('a);
Return the n
-th element of the given list.
The first element (head of the list) is at position 0.
Return None
if the list is too short.
Invalid_argument
if n
is negative.let rev: list('a) => list('a);
List reversal.
let init: (~len: int, ~f: int => 'a) => list('a);
init ~len ~f
is f 0; f 1; ...; f (len-1)
, evaluated left to right.
Invalid_argument
if len < 0
.let append: (list('a), list('a)) => list('a);
Concatenate two lists. Same function as the infix operator @
.
Not tail-recursive (length of the first argument). The @
operator is not tail-recursive either.
let rev_append: (list('a), list('a)) => list('a);
rev_append l1 l2
reverses l1
and concatenates it with l2
.
This is equivalent to (
ListLabels.rev
l1) @ l2
, but rev_append
is
tail-recursive and more efficient.
let concat: list(list('a)) => list('a);
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).
let flatten: list(list('a)) => list('a);
Same as ListLabels.concat
. Not tail-recursive
(length of the argument + length of the longest sub-list).
let equal: (~eq: ('a, 'a) => bool, list('a), list('a)) => bool;
equal eq [a1; ...; an] [b1; ..; bm]
holds when
the two input lists have the same length, and for each
pair of elements ai
, bi
at the same position we have
eq ai bi
.
Note: the eq
function may be called even if the
lists have different length. If you know your equality
function is costly, you may want to check ListLabels.compare_lengths
first.
let compare: (~cmp: ('a, 'a) => int, list('a), list('a)) => int;
compare cmp [a1; ...; an] [b1; ...; bm]
performs
a lexicographic comparison of the two input lists,
using the same 'a -> 'a -> int
interface as compare
:
a1 :: l1
is smaller than a2 :: l2
(negative result)
if a1
is smaller than a2
, or if they are equal (0 result)
and l1
is smaller than l2
[]
is strictly smaller than non-empty listsNote: the cmp
function will be called even if the lists have
different lengths.
let iter: (~f: 'a => unit, list('a)) => unit;
iter ~f [a1; ...; an]
applies function f
in turn to
a1; ...; an
. It is equivalent to
begin f a1; f a2; ...; f an; () end
.
let iteri: (~f: (int, 'a) => unit, list('a)) => 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.
let map: (~f: 'a => 'b, list('a)) => list('b);
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.
let mapi: (~f: (int, 'a) => 'b, list('a)) => list('b);
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. Not tail-recursive.
let rev_map: (~f: 'a => 'b, list('a)) => list('b);
rev_map ~f l
gives the same result as
ListLabels.rev
(
ListLabels.map
f l)
, but is tail-recursive and
more efficient.
let filter_map: (~f: 'a => option('b), list('a)) => list('b);
filter_map ~f l
applies f
to every element of l
, filters
out the None
elements and returns the list of the arguments of
the Some
elements.
let concat_map: (~f: 'a => list('b), list('a)) => list('b);
concat_map ~f l
gives the same result as
ListLabels.concat
(
ListLabels.map
f l)
. Tail-recursive.
let fold_left_map:
(~f: ('a, 'b) => ('a, 'c), ~init: 'a, list('b)) => ('a, list('c));
fold_left_map
is a combination of fold_left
and map
that threads an
accumulator through calls to f
.
let fold_left: (~f: ('a, 'b) => 'a, ~init: 'a, list('b)) => 'a;
fold_left ~f ~init [b1; ...; bn]
is
f (... (f (f init b1) b2) ...) bn
.
let fold_right: (~f: ('a, 'b) => 'b, list('a), ~init: 'b) => 'b;
fold_right ~f [a1; ...; an] ~init
is
f a1 (f a2 (... (f an init) ...))
. Not tail-recursive.
let iter2: (~f: ('a, 'b) => unit, list('a), list('b)) => unit;
iter2 ~f [a1; ...; an] [b1; ...; bn]
calls in turn
f a1 b1; ...; f an bn
.
Invalid_argument
if the two lists are determined
to have different lengths.let map2: (~f: ('a, 'b) => 'c, list('a), list('b)) => list('c);
map2 ~f [a1; ...; an] [b1; ...; bn]
is
[f a1 b1; ...; f an bn]
.
Invalid_argument
if the two lists are determined
to have different lengths. Not tail-recursive.let rev_map2: (~f: ('a, 'b) => 'c, list('a), list('b)) => list('c);
rev_map2 ~f l1 l2
gives the same result as
ListLabels.rev
(
ListLabels.map2
f l1 l2)
, but is tail-recursive and
more efficient.
let fold_left2:
(~f: ('a, 'b, 'c) => 'a, ~init: 'a, list('b), list('c)) => 'a;
fold_left2 ~f ~init [a1; ...; an] [b1; ...; bn]
is
f (... (f (f init a1 b1) a2 b2) ...) an bn
.
Invalid_argument
if the two lists are determined
to have different lengths.let fold_right2:
(~f: ('a, 'b, 'c) => 'c, list('a), list('b), ~init: 'c) => 'c;
fold_right2 ~f [a1; ...; an] [b1; ...; bn] ~init
is
f a1 b1 (f a2 b2 (... (f an bn init) ...))
.
Invalid_argument
if the two lists are determined
to have different lengths. Not tail-recursive.let for_all: (~f: 'a => bool, list('a)) => bool;
for_all ~f [a1; ...; an]
checks if all elements of the list
satisfy the predicate f
. That is, it returns
(f a1) && (f a2) && ... && (f an)
for a non-empty list and
true
if the list is empty.
let exists: (~f: 'a => bool, list('a)) => bool;
exists ~f [a1; ...; an]
checks if at least one element of
the list satisfies the predicate f
. That is, it returns
(f a1) || (f a2) || ... || (f an)
for a non-empty list and
false
if the list is empty.
let for_all2: (~f: ('a, 'b) => bool, list('a), list('b)) => bool;
Same as ListLabels.for_all
, but for a two-argument predicate.
Invalid_argument
if the two lists are determined
to have different lengths.let exists2: (~f: ('a, 'b) => bool, list('a), list('b)) => bool;
Same as ListLabels.exists
, but for a two-argument predicate.
Invalid_argument
if the two lists are determined
to have different lengths.let mem: ('a, ~set: list('a)) => bool;
mem a ~set
is true if and only if a
is equal
to an element of set
.
let memq: ('a, ~set: list('a)) => bool;
Same as ListLabels.mem
, but uses physical equality instead of structural
equality to compare list elements.
let find: (~f: 'a => bool, list('a)) => 'a;
find ~f l
returns the first element of the list l
that satisfies the predicate f
.
Not_found
if there is no value that satisfies f
in the
list l
.let find_opt: (~f: 'a => bool, list('a)) => option('a);
find ~f l
returns the first element of the list l
that satisfies the predicate f
.
Returns None
if there is no value that satisfies f
in the
list l
.
let find_map: (~f: 'a => option('b), list('a)) => option('b);
find_map ~f l
applies f
to the elements of l
in order,
and returns the first result of the form Some v
, or None
if none exist.
let filter: (~f: 'a => bool, list('a)) => list('a);
filter ~f l
returns all the elements of the list l
that satisfy the predicate f
. The order of the elements
in the input list is preserved.
let find_all: (~f: 'a => bool, list('a)) => list('a);
find_all
is another name for ListLabels.filter
.
let filteri: (~f: (int, 'a) => bool, list('a)) => list('a);
Same as ListLabels.filter
, but the predicate is applied to the index of
the element as first argument (counting from 0), and the element
itself as second argument.
let partition: (~f: 'a => bool, list('a)) => (list('a), list('a));
partition ~f l
returns a pair of lists (l1, l2)
, where
l1
is the list of all the elements of l
that
satisfy the predicate f
, and l2
is the list of all the
elements of l
that do not satisfy f
.
The order of the elements in the input list is preserved.
let partition_map:
(~f: 'a => Either.t('b, 'c), list('a)) => (list('b), list('c));
partition_map f l
returns a pair of lists (l1, l2)
such that,
for each element x
of the input list l
:
f x
is Left y1
, then y1
is in l1
, andf x
is Right y2
, then y2
is in l2
.The output elements are included in l1
and l2
in the same
relative order as the corresponding input elements in l
.
In particular, partition_map (fun x -> if f x then Left x else Right x) l
is equivalent to partition f l
.
let assoc: ('a, list(('a, 'b))) => '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
.
Not_found
if there is no value associated with a
in the
list l
.let assoc_opt: ('a, list(('a, 'b))) => option('b);
assoc_opt a l
returns the value associated with key a
in the list of
pairs l
. That is,
assoc_opt a [ ...; (a,b); ...] = Some b
if (a,b)
is the leftmost binding of a
in list l
.
Returns None
if there is no value associated with a
in the
list l
.
let assq: ('a, list(('a, 'b))) => 'b;
Same as ListLabels.assoc
, but uses physical equality instead of
structural equality to compare keys.
let assq_opt: ('a, list(('a, 'b))) => option('b);
Same as ListLabels.assoc_opt
, but uses physical equality instead of
structural equality to compare keys.
let mem_assoc: ('a, ~map: list(('a, 'b))) => bool;
Same as ListLabels.assoc
, but simply return true
if a binding exists,
and false
if no bindings exist for the given key.
let mem_assq: ('a, ~map: list(('a, 'b))) => bool;
Same as ListLabels.mem_assoc
, but uses physical equality instead of
structural equality to compare keys.
let remove_assoc: ('a, list(('a, 'b))) => list(('a, 'b));
remove_assoc a l
returns the list of
pairs l
without the first pair with key a
, if any.
Not tail-recursive.
let remove_assq: ('a, list(('a, 'b))) => list(('a, 'b));
Same as ListLabels.remove_assoc
, but uses physical equality instead
of structural equality to compare keys. Not tail-recursive.
let split: list(('a, 'b)) => (list('a), list('b));
Transform a list of pairs into a pair of lists:
split [(a1,b1); ...; (an,bn)]
is ([a1; ...; an], [b1; ...; bn])
.
Not tail-recursive.
let combine: (list('a), list('b)) => list(('a, 'b));
Transform a pair of lists into a list of pairs:
combine [a1; ...; an] [b1; ...; bn]
is
[(a1,b1); ...; (an,bn)]
.
Invalid_argument
if the two lists
have different lengths. Not tail-recursive.let sort: (~cmp: ('a, 'a) => int, list('a)) => list('a);
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,
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.
let stable_sort: (~cmp: ('a, 'a) => int, list('a)) => list('a);
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.
let fast_sort: (~cmp: ('a, 'a) => int, list('a)) => list('a);
Same as ListLabels.sort
or ListLabels.stable_sort
, whichever is
faster on typical input.
let sort_uniq: (~cmp: ('a, 'a) => int, list('a)) => list('a);
Same as ListLabels.sort
, but also remove duplicates.
let merge: (~cmp: ('a, 'a) => int, list('a), list('a)) => list('a);
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 containing 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).
let to_seq: list('a) => Seq.t('a);
Iterate on the list.
let of_seq: Seq.t('a) => list('a);
Create a list from the iterator.