Module Base__Import0.ListLabels
val hd : 'a list -> 'a
Return the first element of the given list. Raise
Failure "hd"
if the list is empty.
val compare_lengths : 'a list -> 'b list -> int
Compare the lengths of two lists.
compare_lengths l1 l2
is equivalent tocompare (length l1) (length l2)
, except that the computation stops after itering on the shortest list.- since
- 4.05.0
val compare_length_with : 'a list -> len:int -> int
Compare the length of a list to an integer.
compare_length_with l n
is equivalent tocompare (length l) n
, except that the computation stops after at mostn
iterations on the list.- since
- 4.05.0
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. RaiseFailure "nth"
if the list is too short. RaiseInvalid_argument "List.nth"
ifn
is negative.
val nth_opt : 'a list -> int -> 'a option
Return the
n
-th element of the given list. The first element (head of the list) is at position 0. ReturnNone
if the list is too short. RaiseInvalid_argument "List.nth"
ifn
is negative.- since
- 4.05
val init : len:int -> f:(int -> 'a) -> 'a list
List.init len f
isf 0; f 1; ...; f (len-1)
, evaluated left to right.- raises Invalid_argument
if
len < 0
.
- since
- 4.06.0
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
reversesl1
and concatenates it withl2
. This is equivalent to(
List
.revl1) @ l2
, butrev_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
List.iter f [a1; ...; an]
applies functionf
in turn toa1; ...; an
. It is equivalent tobegin f a1; f a2; ...; f an; () end
.
val iteri : f:(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 : f:('a -> 'b) -> 'a list -> 'b list
List.map f [a1; ...; an]
applies functionf
toa1, ..., an
, and builds the list[f a1; ...; f an]
with the results returned byf
. Not tail-recursive.
val mapi : f:(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.- since
- 4.00.0
val rev_map : f:('a -> 'b) -> 'a list -> 'b list
List.rev_map f l
gives the same result asList
.rev(
List
.mapf l)
, but is tail-recursive and more efficient.
val filter_map : f:('a -> 'b option) -> 'a list -> 'b list
filter_map f l
appliesf
to every element ofl
, filters out theNone
elements and returns the list of the arguments of theSome
elements.- since
- 4.08.0
Iterators on two lists
val iter2 : f:('a -> 'b -> unit) -> 'a list -> 'b list -> unit
List.iter2 f [a1; ...; an] [b1; ...; bn]
calls in turnf a1 b1; ...; f an bn
. RaiseInvalid_argument
if the two lists are determined to have different lengths.
val map2 : f:('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list
List.map2 f [a1; ...; an] [b1; ...; bn]
is[f a1 b1; ...; f an bn]
. RaiseInvalid_argument
if the two lists are determined to have different lengths. Not tail-recursive.
val rev_map2 : f:('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list
List.rev_map2 f l1 l2
gives the same result asList
.rev(
List
.map2f l1 l2)
, but is tail-recursive and more efficient.
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 predicatep
. 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 predicatep
. That is, it returns(p a1) || (p a2) || ... || (p an)
.
val for_all2 : f:('a -> 'b -> bool) -> 'a list -> 'b list -> bool
Same as
List
.for_all, but for a two-argument predicate. RaiseInvalid_argument
if the two lists are determined to have different lengths.
List searching
val find : f:('a -> bool) -> 'a list -> 'a
find p l
returns the first element of the listl
that satisfies the predicatep
. RaiseNot_found
if there is no value that satisfiesp
in the listl
.
val find_opt : f:('a -> bool) -> 'a list -> 'a option
find p l
returns the first element of the listl
that satisfies the predicatep
. ReturnsNone
if there is no value that satisfiesp
in the listl
.- since
- 4.05
val filter : f:('a -> bool) -> 'a list -> 'a list
filter p l
returns all the elements of the listl
that satisfy the predicatep
. The order of the elements in the input list is preserved.
val partition : f:('a -> bool) -> 'a list -> 'a list * 'a list
partition p l
returns a pair of lists(l1, l2)
, wherel1
is the list of all the elements ofl
that satisfy the predicatep
, andl2
is the list of all the elements ofl
that do not satisfyp
. 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 keya
in the list of pairsl
. That is,assoc a [ ...; (a,b); ...] = b
if(a,b)
is the leftmost binding ofa
in listl
. RaiseNot_found
if there is no value associated witha
in the listl
.
val assoc_opt : 'a -> ('a * 'b) list -> 'b option
assoc_opt a l
returns the value associated with keya
in the list of pairsl
. That is,assoc a [ ...; (a,b); ...] = b
if(a,b)
is the leftmost binding ofa
in listl
. ReturnsNone
if there is no value associated witha
in the listl
.- since
- 4.05
val assq : 'a -> ('a * 'b) list -> 'b
Same as
List
.assoc, but uses physical equality instead of structural equality to compare keys.
val assq_opt : 'a -> ('a * 'b) list -> 'b option
Same as
List
.assoc_opt, but uses physical equality instead of structural equality to compare keys.- since
- 4.05.0
val mem_assoc : 'a -> map:('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 -> map:('a * 'b) list -> bool
Same as
List
.mem_assoc, but uses physical equality instead of structural equality to compare keys.
Lists of pairs
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,
Stdlib.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 : cmp:('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 : cmp:('a -> 'a -> int) -> 'a list -> 'a list
Same as
List
.sort orList
.stable_sort, whichever is faster on typical input.
val sort_uniq : cmp:('a -> 'a -> int) -> 'a list -> 'a list
Same as
List
.sort, but also remove duplicates.- since
- 4.03.0
val merge : cmp:('a -> 'a -> int) -> 'a list -> 'a list -> 'a list
Merge two lists: Assuming that
l1
andl2
are sorted according to the comparison functioncmp
,merge cmp l1 l2
will return a sorted list containing all the elements ofl1
andl2
. If several elements compare equal, the elements ofl1
will be before the elements ofl2
. Not tail-recursive (sum of the lengths of the arguments).
Iterators
val to_seq : 'a list -> 'a Seq.t
Iterate on the list
- since
- 4.07
val of_seq : 'a Seq.t -> 'a list
Create a list from the iterator
- since
- 4.07