A reference to some Elixir language syntax for types. Remember that Elixir data structures are all immutable.
Atoms
Leading semicolon
:white :black :red :ok :error
Boolean values true and false are atoms :true and :false. The same for nil and :nil.
Linked List
Square brackets
[ 1, 2, 3 ] [ "foo", "bar" ] [ 10, "x", true ]
Common functions and operators:
| Function or Operator | Result |
|---|---|
length([ "x", "y" ]) | 2 |
[1, 2] ++ [3, 4, 5] | [1, 2, 3, 4, 5] |
[1, 2, 3, 4] -- [2, 4] | [1, 3] |
hd([1, 2, 3, 4]) | 1 |
tl([1, 2, 3, 4]) | [2, 3, 4] |
Tuples
Curly brackets
{ :error, "Error message" }
{ 1, 2, 3 }
{ true, false, "text"}
{ true, true, "One", "One" }
Common functions:
| Function | Result |
|---|---|
elem({ :ok, "OK" }, 1) | "OK" |
put_elem({ "first", "third" }, 1, "second") | {"first", "second"} |
Other functions are in the Tuple module, for example:
| Function | Result |
Tuple.append({ 1, 2, 3 }, 4) | {1, 2, 3, 4} |
Tuple.insert_at({1, 2, 3}, 1, 1.5) | {1, 1.5, 2, 3} |
Tuple.delete_at({1, 2, 3}, 1) | {1, 3} |
Keyword list
List of tuples with two values and the first one is an atom. A simple key-map data structure. The keys are atoms, ordered and can be duplicated.
[ { :k1, 1 }, { :k2, 2 } ]
Special syntax:
[ k1: 1, k2: 2 ]
See the correct place for the semicolon, from :k1 to k1:
To access a key you can use square brackets:
tl = [ first: "first", second: "second" ] tl[:first] # The result is: "first"
When a KL is used as the last argument of a function, the square brackets are optional:
example_fun first_param, k1: 1, k2: 2
example_fun(first_param, k1: 1, k2: 2)
example_fun(first_param, [ k1: 1, k2: 2 ])
example_fun(first_param, [ { :k1, 1 }, { :k2, 2 } ])
To manipulate a KL there is the Keyword module but remember that they are lists.
Maps
The real key-map data structure in Elixir.
# Standard syntax
map = %{ :k => 1, 100 => "one hundred" }
# If all the keys are atoms
map2 = %{ k1: 1, k2: 2 }
# Syntax error
map3 = %{ k1: 1, :k2 => 2 }
The :k atom and the number 100 are the keys; the number 1 and one hundred are the values.
| Operation | Result |
|---|---|
map[:k] | 1 |
map[100] | "one hundred" |
%{ map | :k => "ten" } | %{100 => "one hundred", :k => "ten"} |
%{ map | :not_exists => "..." } | (KeyError) key :not_exists not found |
map.k | 1 |
map2.k2 | 2 |