Elixirの対話モードでキーワードリストとマップの動作を確認してみた

概要

Elixirの対話モードでキーワードリストとマップの動作を確認してみました。以下のページを参考にしました。

対話モードで実行

以下のコマンドを実行しました。

$ iex
Erlang/OTP 24 [erts-12.2.1] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [jit]

Interactive Elixir (1.12.2) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)> list = [{:a, 1}, {:b, 2}]
[a: 1, b: 2]
iex(2)> list == [a: 1, b: 2]
true
iex(3)> list ++ [c: 3]
[a: 1, b: 2, c: 3]
iex(4)> [a: 0] ++ list
[a: 0, a: 1, b: 2]
iex(5)> new_list = [a: 0] ++ list
[a: 0, a: 1, b: 2]
iex(6)> new_list[:a]
0
iex(7)> query = from w in Weather,
...(7)> where: w.prcp > 0,
...(7)> where: w.temp < 20,
...(7)> select: w
** (CompileError) iex:7: undefined function from/2

iex(7)> if(false, do: :this, else: :that)
:that
iex(8)> if(false, [do: :this, else: :that])
:that
iex(9)> if(false, [{:do, :this}, {:else, :that}])
:that
iex(10)> [a: a] = [a: 1]
[a: 1]
iex(11)> a
1
iex(12)> [a: a] = [a: 1, b: 2]
** (MatchError) no match of right hand side value: [a: 1, b: 2]

iex(12)> [b: b, a: a] = [a: 1, b: 2]
** (MatchError) no match of right hand side value: [a: 1, b: 2]

iex(12)> map = %{:a => 1, 2 => :b}
%{2 => :b, :a => 1}
iex(13)> map[:a]
1
iex(14)> map[2]
:b
iex(15)> map[:c]
nil
iex(16)> %{} = %{:a => 1, 2 => :b}
%{2 => :b, :a => 1}
iex(17)> %{:a => a} = %{2 => :b, :a => 1}
%{2 => :b, :a => 1}
iex(18)> a
1
iex(19)> %{:c => c} = %{:a => 1, 2 => :b}
** (MatchError) no match of right hand side value: %{2 => :b, :a => 1}

iex(19)> n = 1
1
iex(20)> map = %{n => :one}
%{1 => :one}
iex(21)> map[n]
:one
iex(22)> %{^n => :one} = %{1 => :one, 2 => :two, 3 => :three}
%{1 => :one, 2 => :two, 3 => :three}
iex(23)> map = %{:a => 1, 2 => :b}
%{2 => :b, :a => 1}
iex(24)> Map.get(map, :a)
1
iex(25)> Map.put(map, :c, 3)
%{2 => :b, :a => 1, :c => 3}
iex(26)> Map.to_list(map)
[{2, :b}, {:a, 1}]
iex(27)> map = %{:a => 1, 2 => :b}
%{2 => :b, :a => 1}
iex(28)> %{map | 2 => :two}
%{2 => :two, :a => 1}
iex(29)> %{map | :c => 3}
** (KeyError) key :c not found in: %{2 => :b, :a => 1}
    (stdlib 3.17) :maps.update(:c, 3, %{2 => :b, :a => 1})
    (stdlib 3.17) erl_eval.erl:256: anonymous fn/2 in :erl_eval.expr/5
    (stdlib 3.17) lists.erl:1267: :lists.foldl/3
iex(29)> map = %{:a => 1, 2 => :b}
%{2 => :b, :a => 1}
iex(30)> Map.put(map, :c, 3)
%{2 => :b, :a => 1, :c => 3}
iex(31)> %{:a => 1, 2 => :b, :a => :one}
warning: key :a will be overridden in map
  iex:31

%{2 => :b, :a => :one}
iex(32)> %{:a => 1, :b => 2}
%{a: 1, b: 2}
iex(33)> map = %{:a => 1, 2 => :b}
%{2 => :b, :a => 1}
iex(34)> map.a
1
iex(35)> map.2
** (SyntaxError) iex:35:5: syntax error before: "2"

iex(35)> map[2]
:b
iex(36)> map.c
** (KeyError) key :c not found in: %{2 => :b, :a => 1}

iex(36)> users = [
...(36)> john: %{name: "John", age: 27, languages: ["Erlang", "Ruby", "Elixir"]},
...(36)> mary: %{name: "Mary", age: 29, languages: ["Elixir", "F#", "Clojure"]}
...(36)> ]
[
  john: %{age: 27, languages: ["Erlang", "Ruby", "Elixir"], name: "John"},
  mary: %{age: 29, languages: ["Elixir", "F#", "Clojure"], name: "Mary"}
]
iex(37)> users[:mary]
%{age: 29, languages: ["Elixir", "F#", "Clojure"], name: "Mary"}
iex(38)> users[:john].age
27
iex(39)> users = put_in(users[:john].age, 31)
[
  john: %{age: 31, languages: ["Erlang", "Ruby", "Elixir"], name: "John"},
  mary: %{age: 29, languages: ["Elixir", "F#", "Clojure"], name: "Mary"}
]
iex(40)> users[:john].age
31
iex(41)> users = update_in(users[:mary].languages, fn languages ->
...(41)> List.delete(languages, "Clojure")
...(41)> end)
[
  john: %{age: 31, languages: ["Erlang", "Ruby", "Elixir"], name: "John"},
  mary: %{age: 29, languages: ["Elixir", "F#"], name: "Mary"}
]
iex(42)> users[:mary].languages
["Elixir", "F#"]
iex(43)> 

まとめ

何かの役に立てばと。