Elixir v1.3.4 List View Source
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.
Charlists
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'}]
Link to this section Summary
Functions
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
Link to this section Functions
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.
Examples
iex> List.delete([1, 2, 3], 1)
[2, 3]
iex> List.delete([1, 2, 2, 3], 2)
[1, 2, 3]
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.
Examples
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.
Examples
iex> List.duplicate("hello", 3)
["hello", "hello", "hello"]
iex> List.duplicate([1, 2], 2)
[[1, 2], [1, 2]]
Returns the first element in list
or nil
if list
is empty.
Examples
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.
Examples
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.
Examples
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.
Examples
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.
Examples
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.
Examples
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.
Examples
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
.
Examples
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
.
Examples
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.
Examples
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.
Examples
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.
Examples
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.
Examples
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
Returns the last element in list
or nil
if list
is empty.
Examples
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.
Examples
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]
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.
Examples
iex> List.to_atom('elixir')
:elixir
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.
Examples
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
Returns the float whose text representation is charlist
.
Inlined by the compiler.
Examples
iex> List.to_float('2.2017764e+0')
2.2017764
Returns an integer whose text representation is charlist
.
Inlined by the compiler.
Examples
iex> List.to_integer('123')
123
Returns an integer whose text representation is charlist
in base base
.
Inlined by the compiler.
Examples
iex> List.to_integer('3FF', 16)
1023
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.
Examples
iex> List.to_string([0x00E6, 0x00DF])
"æß"
iex> List.to_string([0x0061, "bc"])
"abc"
Converts a list to a tuple.
Inlined by the compiler.
Examples
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.
Examples
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]
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.
Examples
iex> List.wrap("hello")
["hello"]
iex> List.wrap([1, 2, 3])
[1, 2, 3]
iex> List.wrap(nil)
[]