Specialized functions that only work on lists.
In general, favor using the Enum
API instead of List
.
Index access for list is linear. Negative indexes are also supported but they imply the list will be iterated twice, one to calculate the proper index and another to perform the operation.
A decision was taken to delegate most functions to Erlang’s standard library but follow Elixir’s convention of receiving the subject (in this case, a list) as the first argument.
If a list is made of non-negative integers, it can also be called as a charlist. Elixir uses single quotes to define charlists:
iex> 'héllo'
[104, 233, 108, 108, 111]
In particular, charlists may be printed back in single quotes if they contain only ASCII-printable codepoints:
iex> 'abc'
'abc'
The rationale behind this behaviour is to better support Erlang libraries which may return text as charlists instead of Elixir strings. One example of such functions is Application.loaded_applications
:
Application.loaded_applications
#=> [{:stdlib, 'ERTS CXC 138 10', '2.6'},
{:compiler, 'ERTS CXC 138 10', '6.0.1'},
{:elixir, 'elixir', '1.0.0'},
{:kernel, 'ERTS CXC 138 10', '4.1'},
{:logger, 'logger', '1.0.0'}]
Deletes the given item from the list. Returns a list without the item. If the item occurs more than once in the list, just the first occurrence is removed
Produces a new list by removing the value at the specified index
. Negative indices indicate an offset from the end of the list. If index
is out of bounds, the original list
is returned
Duplicates the given element n
times in a list
Returns the first element in list
or nil
if list
is empty
Flattens the given list
of nested lists
Flattens the given list
of nested lists. The list tail
will be added at the end of the flattened list
Folds (reduces) the given list from the left with a function. Requires an accumulator
Folds (reduces) the given list from the right with a function. Requires an accumulator
Returns a list with value
inserted at the specified index
. Note that index
is capped at the list length. Negative indices indicate an offset from the end of the list
Receives a list of tuples and deletes the first tuple where the item at position
matches the given key
. Returns the new list
Receives a list of tuples and returns the first tuple where the item at position
in the tuple matches the given key
Receives a list of tuples and returns true
if there is a tuple where the item at position
in the tuple matches the given key
Receives a list of tuples and replaces the item identified by key
at position
if it exists
Receives a list of tuples and sorts the items at position
of the tuples. The sort is stable
Receives a list of tuples and replaces the item identified by key
at position
. If the item does not exist, it is added to the end of the list
Receives a list
of tuples and returns the first tuple where the element at position
in the tuple matches the given key
, as well as the list
without found tuple
Returns the last element in list
or nil
if list
is empty
Returns a list with a replaced value at the specified index
. Negative indices indicate an offset from the end of the list. If index
is out of bounds, the original list
is returned
Converts a charlist to an atom
Converts a charlist to an existing atom. Raises an ArgumentError
if the atom does not exist
Returns the float whose text representation is charlist
Returns an integer whose text representation is charlist
Returns an integer whose text representation is charlist
in base base
Converts a list of integers representing codepoints, lists or strings into a string
Converts a list to a tuple
Returns a list with an updated value at the specified index
. Negative indices indicate an offset from the end of the list. If index
is out of bounds, the original list
is returned
Wraps the argument in a list. If the argument is already a list, returns the list. If the argument is nil
, returns an empty list
Zips corresponding elements from each list in list_of_lists
delete(list, any) :: list
Deletes the given item from the list. Returns a list without the item. If the item occurs more than once in the list, just the first occurrence is removed.
iex> List.delete([1, 2, 3], 1)
[2, 3]
iex> List.delete([1, 2, 2, 3], 2)
[1, 2, 3]
delete_at(list, integer) :: list
Produces a new list by removing the value at the specified index
. Negative indices indicate an offset from the end of the list. If index
is out of bounds, the original list
is returned.
iex> List.delete_at([1, 2, 3], 0)
[2, 3]
iex> List.delete_at([1, 2, 3], 10)
[1, 2, 3]
iex> List.delete_at([1, 2, 3], -1)
[1, 2]
duplicate(elem, non_neg_integer) :: [elem] when elem: var
Duplicates the given element n
times in a list.
iex> List.duplicate("hello", 3)
["hello", "hello", "hello"]
iex> List.duplicate([1, 2], 2)
[[1, 2], [1, 2]]
first([elem]) :: nil | elem when elem: var
Returns the first element in list
or nil
if list
is empty.
iex> List.first([])
nil
iex> List.first([1])
1
iex> List.first([1, 2, 3])
1
flatten(deep_list) :: list when deep_list: [any | deep_list]
Flattens the given list
of nested lists.
iex> List.flatten([1, [[2], 3]])
[1, 2, 3]
flatten(deep_list, [elem]) :: [elem] when deep_list: [elem | deep_list], elem: var
Flattens the given list
of nested lists. The list tail
will be added at the end of the flattened list.
iex> List.flatten([1, [[2], 3]], [4, 5])
[1, 2, 3, 4, 5]
foldl([elem], acc, (elem, acc -> acc)) :: acc when elem: var, acc: var
Folds (reduces) the given list from the left with a function. Requires an accumulator.
iex> List.foldl([5, 5], 10, fn(x, acc) -> x + acc end)
20
iex> List.foldl([1, 2, 3, 4], 0, fn(x, acc) -> x - acc end)
2
foldr([elem], acc, (elem, acc -> acc)) :: acc when elem: var, acc: var
Folds (reduces) the given list from the right with a function. Requires an accumulator.
iex> List.foldr([1, 2, 3, 4], 0, fn(x, acc) -> x - acc end)
-2
insert_at(list, integer, any) :: list
Returns a list with value
inserted at the specified index
. Note that index
is capped at the list length. Negative indices indicate an offset from the end of the list.
iex> List.insert_at([1, 2, 3, 4], 2, 0)
[1, 2, 0, 3, 4]
iex> List.insert_at([1, 2, 3], 10, 0)
[1, 2, 3, 0]
iex> List.insert_at([1, 2, 3], -1, 0)
[1, 2, 3, 0]
iex> List.insert_at([1, 2, 3], -10, 0)
[0, 1, 2, 3]
keydelete([tuple], any, non_neg_integer) :: [tuple]
Receives a list of tuples and deletes the first tuple where the item at position
matches the given key
. Returns the new list.
iex> List.keydelete([a: 1, b: 2], :a, 0)
[b: 2]
iex> List.keydelete([a: 1, b: 2], 2, 1)
[a: 1]
iex> List.keydelete([a: 1, b: 2], :c, 0)
[a: 1, b: 2]
keyfind([tuple], any, non_neg_integer, any) :: any
Receives a list of tuples and returns the first tuple where the item at position
in the tuple matches the given key
.
iex> List.keyfind([a: 1, b: 2], :a, 0)
{:a, 1}
iex> List.keyfind([a: 1, b: 2], 2, 1)
{:b, 2}
iex> List.keyfind([a: 1, b: 2], :c, 0)
nil
keymember?([tuple], any, non_neg_integer) :: any
Receives a list of tuples and returns true
if there is a tuple where the item at position
in the tuple matches the given key
.
iex> List.keymember?([a: 1, b: 2], :a, 0)
true
iex> List.keymember?([a: 1, b: 2], 2, 1)
true
iex> List.keymember?([a: 1, b: 2], :c, 0)
false
keyreplace([tuple], any, non_neg_integer, tuple) :: [tuple]
Receives a list of tuples and replaces the item identified by key
at position
if it exists.
iex> List.keyreplace([a: 1, b: 2], :a, 0, {:a, 3})
[a: 3, b: 2]
keysort([tuple], non_neg_integer) :: [tuple]
Receives a list of tuples and sorts the items at position
of the tuples. The sort is stable.
iex> List.keysort([a: 5, b: 1, c: 3], 1)
[b: 1, c: 3, a: 5]
iex> List.keysort([a: 5, c: 1, b: 3], 0)
[a: 5, b: 3, c: 1]
keystore([tuple], any, non_neg_integer, tuple) :: [tuple, ...]
Receives a list of tuples and replaces the item identified by key
at position
. If the item does not exist, it is added to the end of the list.
iex> List.keystore([a: 1, b: 2], :a, 0, {:a, 3})
[a: 3, b: 2]
iex> List.keystore([a: 1, b: 2], :c, 0, {:c, 3})
[a: 1, b: 2, c: 3]
keytake([tuple], any, non_neg_integer) :: {tuple, [tuple]} | nil
Receives a list
of tuples and returns the first tuple where the element at position
in the tuple matches the given key
, as well as the list
without found tuple.
If such a tuple is not found, nil
will be returned.
iex> List.keytake([a: 1, b: 2], :a, 0)
{{:a, 1}, [b: 2]}
iex> List.keytake([a: 1, b: 2], 2, 1)
{{:b, 2}, [a: 1]}
iex> List.keytake([a: 1, b: 2], :c, 0)
nil
last([elem]) :: nil | elem when elem: var
Returns the last element in list
or nil
if list
is empty.
iex> List.last([])
nil
iex> List.last([1])
1
iex> List.last([1, 2, 3])
3
replace_at(list, integer, any) :: list
Returns a list with a replaced value at the specified index
. Negative indices indicate an offset from the end of the list. If index
is out of bounds, the original list
is returned.
iex> List.replace_at([1, 2, 3], 0, 0)
[0, 2, 3]
iex> List.replace_at([1, 2, 3], 10, 0)
[1, 2, 3]
iex> List.replace_at([1, 2, 3], -1, 0)
[1, 2, 0]
iex> List.replace_at([1, 2, 3], -10, 0)
[1, 2, 3]
to_atom(charlist) :: atom
Converts a charlist to an atom.
Currently Elixir does not support conversions from charlists which contains Unicode codepoints greater than 0xFF.
Inlined by the compiler.
iex> List.to_atom('elixir')
:elixir
to_existing_atom(charlist) :: atom
Converts a charlist to an existing atom. Raises an ArgumentError
if the atom does not exist.
Currently Elixir does not support conversions from charlists which contains Unicode codepoints greater than 0xFF.
Inlined by the compiler.
iex> _ = :my_atom
iex> List.to_existing_atom('my_atom')
:my_atom
iex> List.to_existing_atom('this_atom_will_never_exist')
** (ArgumentError) argument error
to_float(charlist) :: float
Returns the float whose text representation is charlist
.
Inlined by the compiler.
iex> List.to_float('2.2017764e+0')
2.2017764
to_integer(charlist) :: integer
Returns an integer whose text representation is charlist
.
Inlined by the compiler.
iex> List.to_integer('123')
123
to_integer(charlist, 2..36) :: integer
Returns an integer whose text representation is charlist
in base base
.
Inlined by the compiler.
iex> List.to_integer('3FF', 16)
1023
to_string(:unicode.charlist) :: String.t
Converts a list of integers representing codepoints, lists or strings into a string.
Notice that this function expects a list of integers representing UTF-8 codepoints. If you have a list of bytes, you must instead use the :binary
module.
iex> List.to_string([0x00E6, 0x00DF])
"æß"
iex> List.to_string([0x0061, "bc"])
"abc"
to_tuple(list) :: tuple
Converts a list to a tuple.
Inlined by the compiler.
iex> List.to_tuple([:share, [:elixir, 163]])
{:share, [:elixir, 163]}
update_at([elem], integer, (elem -> any)) :: list when elem: var
Returns a list with an updated value at the specified index
. Negative indices indicate an offset from the end of the list. If index
is out of bounds, the original list
is returned.
iex> List.update_at([1, 2, 3], 0, &(&1 + 10))
[11, 2, 3]
iex> List.update_at([1, 2, 3], 10, &(&1 + 10))
[1, 2, 3]
iex> List.update_at([1, 2, 3], -1, &(&1 + 10))
[1, 2, 13]
iex> List.update_at([1, 2, 3], -10, &(&1 + 10))
[1, 2, 3]
wrap(list | any) :: list
Wraps the argument in a list. If the argument is already a list, returns the list. If the argument is nil
, returns an empty list.
iex> List.wrap("hello")
["hello"]
iex> List.wrap([1, 2, 3])
[1, 2, 3]
iex> List.wrap(nil)
[]
zip([list]) :: [tuple]
Zips corresponding elements from each list in list_of_lists
.
The zipping finishes as soon as any list terminates.
iex> List.zip([[1, 2], [3, 4], [5, 6]])
[{1, 3, 5}, {2, 4, 6}]
iex> List.zip([[1, 2], [3], [5, 6]])
[{1, 3, 5}]
© 2012–2017 Plataformatec
Licensed under the Apache License, Version 2.0.
https://hexdocs.pm/elixir/1.3.3/List.html