chapter 3

chapter3/excersises.ex

@@ -0,0 +1,43 @@
+defmodule Exercise do
+  def run() do
+    pboss = spawn(ProcessBoss, :loop, [])
+    pid1 = spawn(Process1, :loop, [])
+    pid2 = spawn(Process2, :loop, [])
+
+    send pid1, {pboss, :ping}
+    send pid2, {pboss, :pong}
+  end
+end
+
+defmodule ProcessBoss do
+  def loop do
+    receive do
+      {:ok, msg, from: from} -> IO.inspect("#{from} says #{msg}")
+      _ -> IO.puts "Unknow Message"
+    end
+    loop()
+  end
+end
+
+defmodule Process1 do
+  def loop do
+    receive do
+      {sender_pid, :ping} ->
+        send(sender_pid, {:ok, :pong, from: :ping})
+      _ ->
+        IO.puts "Unknow Message"
+    end
+    loop()
+  end
+end
+
+defmodule Process2 do
+  def loop do
+    receive do
+      {sender_pid, :pong} ->
+        send(sender_pid, {:ok, :ping, from: :pong})
+      _ -> IO.puts "Unknow Message"
+    end
+    loop()
+  end
+end

chapter3/metex/.formatter.exs

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+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

chapter3/metex/.gitignore

@@ -0,0 +1,25 @@
+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where 3rd-party dependencies like ExDoc output generated docs.
+/doc/
+
+# Ignore .fetch files in case you like to edit your project deps locally.
+/.fetch
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+metex-*.tar
+
+.elixir_ls/

chapter3/metex/README.md

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+# Metex
+
+**TODO: Add description**
+
+## Installation
+
+If [available in Hex](https://hex.pm/docs/publish), the package can be installed
+by adding `metex` to your list of dependencies in `mix.exs`:
+
+```elixir
+def deps do
+  [
+    {:metex, "~> 0.1.0"}
+  ]
+end
+```
+
+Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_doc)
+and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
+be found at [https://hexdocs.pm/metex](https://hexdocs.pm/metex).
+

chapter3/metex/config/config.exs

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+# This file is responsible for configuring your application
+# and its dependencies with the aid of the Mix.Config module.
+use Mix.Config
+
+# This configuration is loaded before any dependency and is restricted
+# to this project. If another project depends on this project, this
+# file won't be loaded nor affect the parent project. For this reason,
+# if you want to provide default values for your application for
+# 3rd-party users, it should be done in your "mix.exs" file.
+
+# You can configure your application as:
+#
+#     config :metex, key: :value
+#
+# and access this configuration in your application as:
+#
+#     Application.get_env(:metex, :key)
+#
+# You can also configure a 3rd-party app:
+#
+#     config :logger, level: :info
+#
+
+# It is also possible to import configuration files, relative to this
+# directory. For example, you can emulate configuration per environment
+# by uncommenting the line below and defining dev.exs, test.exs and such.
+# Configuration from the imported file will override the ones defined
+# here (which is why it is important to import them last).
+#
+#     import_config "#{Mix.env()}.exs"

chapter3/metex/lib/coordinator.ex

@@ -0,0 +1,16 @@
+defmodule Metex.Coordinator do
+  def loop(results \\ [], results_expected) do
+    receive do
+      {:ok, result} ->
+        new_results = [result | results]
+        if results_expected == Enum.count(new_results) do
+          send self(), :exit
+        end
+        loop(new_results, results_expected)
+      :exit ->
+        IO.puts(results |> Enum.sort |> Enum.join(", "))
+      _ ->
+        loop(results, results_expected)
+    end
+  end
+end

chapter3/metex/lib/metex.ex

@@ -0,0 +1,14 @@
+defmodule Metex do
+  def temperature_of(cities) do
+    coordinator_pid =
+      spawn(Metex.Coordinator, :loop, [[], Enum.count(cities)])
+
+    cities |> Enum.each(fn city ->
+      worker_pid = spawn(Metex.Worker, :loop, [])
+      send worker_pid, {coordinator_pid, city}
+    end)
+  end
+end
+
+# cities = ["Singapore", "Monaco", "Vatican City", "Hong Kong", "Macau"]
+# Metex.temperature_of(cities)

chapter3/metex/lib/worker.ex

@@ -0,0 +1,59 @@
+defmodule Metex.Worker do
+  def loop do
+    receive do
+      {sender_pid, location} ->
+        send(sender_pid, {:ok, temperature_of(location)})
+      _ ->
+        IO.puts "don't know how to process this message"
+    end
+    loop()
+  end
+
+  def temperature_of(location) do
+    result = url_for(location) |> HTTPoison.get |> parse_response
+    case result do
+      {:ok, temp} ->
+        "#{location}: #{temp}°C"
+      :error ->
+        "#{location}: not found"
+    end
+  end
+
+  defp url_for(location) do
+    location = URI.encode(location)
+    "http://api.openweathermap.org/data/2.5/weather?q=#{location}&appid=#{apikey()}"
+  end
+
+  defp parse_response({:ok, %HTTPoison.Response{body: body, status_code: 200}}) do
+    body |> JSON.decode! |> compute_temperature
+  end
+
+  defp parse_response(_) do
+    :error
+  end
+
+  defp compute_temperature(json) do
+    try do
+      temp = (json["main"]["temp"] - 273.15) |> Float.round(1)
+      {:ok, temp}
+    rescue
+      _ -> :error
+    end
+  end
+
+  defp apikey do
+    "74148f1e51e4ac1feba5e0d04c2a1ec2"
+  end
+end
+
+# cities = ["Singapore", "Monaco", "Vatican City", "Hong Kong", "Macau"]
+
+# Without Processes
+# cities |> Enum.map(fn city -> Metex.Worker.temperature_of(city) end)
+
+# With Processes
+# pid = spawn(Metex.Worker, :loop, [])
+# cities |> Enum.each(fn city ->
+#   pid = spawn(Metex.Worker, :loop, [])
+#   send(pid, {self, city})
+# end)

chapter3/metex/mix.exs

@@ -0,0 +1,30 @@
+defmodule Metex.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :metex,
+      version: "0.1.0",
+      elixir: "~> 1.7",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger, :httpoison]
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      {:httpoison, "~> 1.2.0"},
+      {:json, "~> 1.2"}
+      # {:dep_from_hexpm, "~> 0.3.0"},
+      # {:dep_from_git, git: "https://github.com/elixir-lang/my_dep.git", tag: "0.1.0"},
+    ]
+  end
+end

chapter3/metex/mix.lock

@@ -0,0 +1,12 @@
+%{
+  "certifi": {:hex, :certifi, "2.3.1", "d0f424232390bf47d82da8478022301c561cf6445b5b5fb6a84d49a9e76d2639", [:rebar3], [{:parse_trans, "3.2.0", [hex: :parse_trans, repo: "hexpm", optional: false]}], "hexpm"},
+  "hackney": {:hex, :hackney, "1.13.0", "24edc8cd2b28e1c652593833862435c80661834f6c9344e84b6a2255e7aeef03", [:rebar3], [{:certifi, "2.3.1", [hex: :certifi, repo: "hexpm", optional: false]}, {:idna, "5.1.2", [hex: :idna, repo: "hexpm", optional: false]}, {:metrics, "1.0.1", [hex: :metrics, repo: "hexpm", optional: false]}, {:mimerl, "1.0.2", [hex: :mimerl, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "1.1.1", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}], "hexpm"},
+  "httpoison": {:hex, :httpoison, "1.2.0", "2702ed3da5fd7a8130fc34b11965c8cfa21ade2f232c00b42d96d4967c39a3a3", [:mix], [{:hackney, "~> 1.8", [hex: :hackney, repo: "hexpm", optional: false]}], "hexpm"},
+  "idna": {:hex, :idna, "5.1.2", "e21cb58a09f0228a9e0b95eaa1217f1bcfc31a1aaa6e1fdf2f53a33f7dbd9494", [:rebar3], [{:unicode_util_compat, "0.3.1", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm"},
+  "json": {:hex, :json, "1.2.5", "3682c18c6b07480df2122d0daf5c05457b42c1990f197ce3de53884e8ba834c4", [:mix], [{:benchee, "~> 0.8", [hex: :benchee, repo: "hexpm", optional: true]}, {:benchee_html, "~> 0.1", [hex: :benchee_html, repo: "hexpm", optional: true]}, {:exjsx, "~> 4.0", [hex: :exjsx, repo: "hexpm", optional: true]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:jsone, "~> 1.4", [hex: :jsone, repo: "hexpm", optional: true]}, {:poison, "~> 3.0", [hex: :poison, repo: "hexpm", optional: true]}, {:tiny, "~> 1.0", [hex: :tiny, repo: "hexpm", optional: true]}], "hexpm"},
+  "metrics": {:hex, :metrics, "1.0.1", "25f094dea2cda98213cecc3aeff09e940299d950904393b2a29d191c346a8486", [:rebar3], [], "hexpm"},
+  "mimerl": {:hex, :mimerl, "1.0.2", "993f9b0e084083405ed8252b99460c4f0563e41729ab42d9074fd5e52439be88", [:rebar3], [], "hexpm"},
+  "parse_trans": {:hex, :parse_trans, "3.2.0", "2adfa4daf80c14dc36f522cf190eb5c4ee3e28008fc6394397c16f62a26258c2", [:rebar3], [], "hexpm"},
+  "ssl_verify_fun": {:hex, :ssl_verify_fun, "1.1.1", "28a4d65b7f59893bc2c7de786dec1e1555bd742d336043fe644ae956c3497fbe", [:make, :rebar], [], "hexpm"},
+  "unicode_util_compat": {:hex, :unicode_util_compat, "0.3.1", "a1f612a7b512638634a603c8f401892afbf99b8ce93a45041f8aaca99cadb85e", [:rebar3], [], "hexpm"},
+}

chapter3/metex/test/metex_test.exs

@@ -0,0 +1,8 @@
+defmodule MetexTest do
+  use ExUnit.Case
+  doctest Metex
+
+  test "greets the world" do
+    assert Metex.hello() == :world
+  end
+end

chapter3/metex/test/test_helper.exs

@@ -0,0 +1 @@
+ExUnit.start()