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1 Hello Elixir

2 Basic syntax

3 Pattern Match

Exercise 3-1

# xに1が、yに4が束縛されるようパターンマッチを完成させてください。
[0, x, 2, 3, y, 5] = [0, 1, 2, 3, 4, 5]

x == 1 and y == 4

true

Exercise 3-2

# 3を変数xに束縛
%{c: x} = %{a: 1, b: 2, c: 3}

x == 3

true

Exercise 3-3

# :aを変数x、2.3を変数yに拘束（1と"a"は何にも拘束しない）
[_, x, _, y] = [1, :a, "a", 2.3]

x == :a and y == 2.3

true

Exercise 3-4

# 2を変数x、4を変数y、5～10のリストをzに拘束（1と3は何にも拘束しない）
[1, x, 3, y | z] = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

x == 2 and y == 4 and z == [5, 6, 7, 8, 9, 10]

true

Exercise 3-5

# 1を変数x、4を変数yに拘束
%{a: %{b: x, d: [_, y, _]}} = %{a: %{b: 1, c: 2, d: [3, 4, 5]}}

x == 1 and y == 4

true

Exercise 3-6

# 複雑なパターンマッチを試してみよう

request = %{
  header: %{
    "x-custom-header": "a8d3981b2"
  },
  body: %{
    first_name: "Alice",
    last_name: "Liddell",
    address: [
      "Westminster",
      "London",
      "England",
      "United Kingdom"
    ]
  }
}

# requestのbodyからfirst_nameとlast_nameを同時に取り出してみよう
%{body: %{first_name: first_name, last_name: last_name}} = request
first_name == "Alice" and last_name == "Liddell"

true

Exercise 3-7

# requestのbodyのaddressは地区、州、構成国、主権国家の順に並んでいる。州(state)と構成国(country)だけ取り出してみよう
%{body: %{address: [_, state, country, _]}} = request

state == "London" and country == "England"

true

4 Function and module

Exercise 4-1

request = %{
  header: %{content_type: "application/json"},
  body: %{target: 21, message_to_you: "This may be the answer of everything."}
}

extract_answer = fn %{body: %{target: value}} -> value * 2 end

extract_answer.(request) == 42

true

Exercise 4-2

func = fn x, y, callback -> callback.(x, y) end

add = &(&1 + &2)
func.(1, 2, add) == 3

true

Exercise 4-3

# implement Name module!

defmodule Name do
  def get_first_name(%{first_name: value}) do
    value
  end

  def get_last_name(%{last_name: value}) do
    value
  end

  def get_full_name(name_map) do
    "#{get_first_name(name_map)} #{get_last_name(name_map)}"
  end
end

name_map = %{first_name: "Jose", last_name: "Valim"}

Name.get_first_name(name_map) == "Jose" and
  Name.get_last_name(name_map) == "Valim" and
  Name.get_full_name(name_map) == "Jose Valim"

true

5 Control syntax

Exercise 5-1

response = %{status: 400, body: %{message: "Invalid parameter!"}}

result =
  case response do
    %{status: 200, body: body} -> {:ok, body}
    %{status: 400} -> {:error, :bad_request}
    %{status: 404} -> {:error, :not_found}
    %{status: 500} -> {:error, :internal_error}
  end

result == {:error, :bad_request}

true

6 pipe operator with Enum module

7 Use hex packages