Initial Commit

.gitignore

@@ -0,0 +1,18 @@
+# Created by https://www.toptal.com/developers/gitignore/api/elixir
+# Edit at https://www.toptal.com/developers/gitignore?templates=elixir
+
+### Elixir ###
+/_build
+/cover
+/deps
+/doc
+/.fetch
+erl_crash.dump
+*.ez
+*.beam
+/config/*.secret.exs
+.elixir_ls/
+
+### Elixir Patch ###
+
+# End of https://www.toptal.com/developers/gitignore/api/elixir

binary.exs

@@ -0,0 +1,25 @@
+defmodule BinarySearch do
+  def binary_search(_numbers, _key, low, high) when low > high do
+    :not_found
+  end
+
+  @spec binary_search(list, integer, integer, integer) :: integer | :not_found
+  def binary_search(numbers, key, low, high) do
+    md = low + Integer.floor_div(high-low, 2)
+    IO.inspect(md)
+    case elem(numbers, md) do
+      x when x > key -> binary_search(numbers, key, low, md-1)
+      x when x < key -> binary_search(numbers, key, md+1, high)
+      x when x == key -> md
+    end
+  end
+
+  @spec search(tuple, integer) :: {:ok, integer} | :not_found
+  def search(numbers, key) do
+    case binary_search(numbers, key, 0, tuple_size(numbers)-1) do
+      :not_found -> :not_found
+      x -> {:ok, x}
+    end
+  end
+end
+

fibo.exs

@@ -0,0 +1,19 @@
+defmodule Fibonacci do
+  def get(n) when n > 2 do
+    get(n-2) + get(n-1)
+  end
+
+  def get(_n) do 
+    1
+  end
+end
+
+1..10 |> Enum.map(fn i -> IO.puts("Fib #{i} = #{Fibonacci.get(i)}") end)
+1..10 |> Enum.map(&(IO.puts("Fib #{&1} = #{Fibonacci.get(&1)}")))
+for i <- 1..10 do
+  IO.puts("Fib #{i} = #{Fibonacci.get(i)}")
+end
+res = for x <- 1..10, reduce: 0 do
+  acc -> acc + Fibonacci.get(x)
+end
+IO.puts("Somma dei fibonacci da 1 a 10 #{res}")

genserver.exs

@@ -0,0 +1,38 @@
+defmodule Stack do
+  use GenServer
+
+  # Client
+
+  def start_link(default) when is_binary(default) do
+    GenServer.start_link(__MODULE__, default)
+  end
+
+  def push(pid, element) do
+    GenServer.cast(pid, {:push, element})
+  end
+
+  def pop(pid) do
+    GenServer.call(pid, :pop)
+  end
+
+  # Server (callbacks)
+
+  @impl true
+  def init(elements) do
+    initial_state = String.split(elements, ",", trim: true)
+    {:ok, initial_state}
+  end
+
+  @impl true
+  def handle_call(:pop, _from, state) do
+    [to_caller | new_state] = state
+    {:reply, to_caller, new_state}
+  end
+
+  @impl true
+  def handle_cast({:push, element}, state) do
+    new_state = [element | state]
+    {:noreply, new_state}
+  end
+end
+

kv.exs

@@ -0,0 +1,17 @@
+# Key-Value store
+defmodule KV do
+  def start_link do
+    Task.start_link(fn -> loop(%{}) end)
+  end
+
+  defp loop(map) do
+    receive do
+      {:get, key, caller} -> 
+        send(caller, Map.get(map, key))
+        loop(map)
+      {:put, key, value} ->
+        loop(Map.put(map, key, value))
+    end
+  end
+end
+

kv/.formatter.exs

@@ -0,0 +1,4 @@
+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

kv/.gitignore

@@ -0,0 +1,26 @@
+# 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 third-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").
+kv-*.tar
+
+# Temporary files, for example, from tests.
+/tmp/

kv/README.md

@@ -0,0 +1,21 @@
+# KV
+
+**TODO: Add description**
+
+## Installation
+
+If [available in Hex](https://hex.pm/docs/publish), the package can be installed
+by adding `kv` to your list of dependencies in `mix.exs`:
+
+```elixir
+def deps do
+  [
+    {:kv, "~> 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/kv>.
+

kv/lib/kv.ex

@@ -0,0 +1,10 @@
+defmodule KV do
+  use Application
+
+  @impl true
+  def start(_type, _args) do
+    # Anche se non usiamo KV.Supervisor name direttamente,
+    # e' comodo per debug
+    KV.Supervisor.start_link(name: KV.Supervisor)
+  end
+end

kv/lib/kv/bucket.ex

@@ -0,0 +1,33 @@
+defmodule KV.Bucket do
+  use Agent, restart: :temporary
+
+  @doc """
+  Starts a new bucket.
+  """
+  def start_link(_opts) do
+    Agent.start_link(fn -> %{} end)
+  end
+
+  @doc """
+  Gets a value from the `bucket` by `key`.
+  """
+  def get(bucket, key) do
+    Agent.get(bucket, &Map.get(&1, key))
+  end
+
+  @doc """
+  Puts the `value` for the given `key` in the `bucket`.
+  """
+  def put(bucket, key, value) do
+    Agent.update(bucket, &Map.put(&1, key, value))
+  end
+
+  @doc """
+  Deletes `key` from `bucket`.
+
+  Returns the current value of `key`, if `key` exists.
+  """
+  def delete(bucket, key) do
+    Agent.get_and_update(bucket, &Map.pop(&1, key))
+  end
+end

kv/lib/kv/registry.ex

@@ -0,0 +1,69 @@
+defmodule KV.Registry do
+  use GenServer
+
+  # Client API
+  @doc """
+  Starts the registry.
+  """
+  def start_link(opts) do
+    server = Keyword.fetch!(opts, :name)
+    GenServer.start_link(__MODULE__, server, opts)
+  end
+
+  @doc """
+  Looks up the bucket pid for `name` stored in `server`.
+
+  Returns `{:ok, pid}` if the bucket exists, `:error` otherwise.
+  """
+  def lookup(server, name) do
+    case :ets.lookup(server, name) do
+      [{^name, pid}] -> {:ok, pid}
+      [] -> :error
+    end
+  end
+
+  @doc """
+  Ensures there is a bucket associated with the given `name` in `server`.
+  """
+  def create(server, name) do
+    GenServer.call(server, {:create, name})
+  end
+
+  # Server Callbacks
+
+  @impl true
+  def init(table) do
+    # name -> bucket
+    names = :ets.new(table, [:named_table, read_concurrency: true])
+    refs = %{} # ref -> name
+    {:ok, {names, refs}}
+  end
+
+  @impl true
+  def handle_call({:create, name}, _from, {names, refs}) do
+    case lookup(names, name) do
+      {:ok, bucket} ->
+        {:reply, bucket, {names, refs}}
+      :error ->
+        {:ok, bucket} = DynamicSupervisor.start_child(KV.BucketSupervisor, KV.Bucket)
+        ref = Process.monitor(bucket)
+        refs = Map.put(refs, ref, name)
+        :ets.insert(names, {name, bucket})
+        {:reply, bucket, {names, refs}}
+    end
+  end
+
+  @impl true
+  def handle_info({:DOWN, ref, :process, _pid, _reason}, {names, refs}) do
+    {name, refs} = Map.pop(refs, ref)
+    :ets.delete(names, name)
+    {:noreply, {names, refs}}
+  end
+
+  @impl true
+  def handle_info(msg, state) do
+    require Logger
+    Logger.debug("Unexpected message in KV.Registry: #{inspect(msg)}")
+    {:noreply, state}
+  end
+end

kv/lib/kv/supervisor.ex

@@ -0,0 +1,17 @@
+defmodule KV.Supervisor do
+  use Supervisor
+
+  def start_link(opts) do
+    Supervisor.start_link(__MODULE__, :ok, opts)
+  end
+
+  @impl true
+  def init(:ok) do
+    children = [
+      {DynamicSupervisor, name: KV.BucketSupervisor, strategy: :one_for_one},
+      {KV.Registry, name: KV.Registry},
+    ]
+
+    Supervisor.init(children, strategy: :one_for_all)
+  end
+end

kv/mix.exs

@@ -0,0 +1,29 @@
+defmodule KV.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :kv,
+      version: "0.1.0",
+      elixir: "~> 1.17",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger],
+      mod: {KV, []}
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      # {:dep_from_hexpm, "~> 0.3.0"},
+      # {:dep_from_git, git: "https://github.com/elixir-lang/my_dep.git", tag: "0.1.0"}
+    ]
+  end
+end

kv/test/kv/bucket_test.exs

@@ -0,0 +1,15 @@
+defmodule KV.BucketTest do
+  use ExUnit.Case, async: true
+
+  setup do
+    bucket = start_supervised!(KV.Bucket)
+    %{bucket: bucket}
+  end
+
+  test "stores values by key", %{bucket: bucket} do
+    assert KV.Bucket.get(bucket, "milk") == nil
+
+    KV.Bucket.put(bucket, "milk", 3)
+    assert KV.Bucket.get(bucket, "milk") == 3
+  end
+end

kv/test/kv/registry_test.exs

@@ -0,0 +1,42 @@
+defmodule KV.RegistryTest do
+  use ExUnit.Case, async: true
+
+  setup context do
+    _ = start_supervised!({KV.Registry, name: context.test})
+    %{registry: context.test}
+  end
+
+  test "spawns buckets", %{registry: registry} do
+    assert KV.Registry.lookup(registry, "shopping") == :error
+
+    KV.Registry.create(registry, "shopping")
+    assert {:ok, bucket} = KV.Registry.lookup(registry, "shopping")
+
+    KV.Bucket.put(bucket, "milk", 1)
+    assert KV.Bucket.get(bucket, "milk") == 1
+  end
+
+  test "removes buckets on exit", %{registry: registry} do
+    KV.Registry.create(registry, "shopping")
+    {:ok, bucket} = KV.Registry.lookup(registry, "shopping")
+    Agent.stop(bucket)
+    # Do a call to ensure the registry processed the DOWN message
+    _ = KV.Registry.create(registry, "bogus")
+    assert KV.Registry.lookup(registry, "shopping") == :error
+  end
+
+  test "removes bucket on crash", %{registry: registry} do
+    KV.Registry.create(registry, "shopping")
+    {:ok, bucket} = KV.Registry.lookup(registry, "shopping")
+
+    # Stop the bucket with non-normal reason
+    # If a process terminates with a reason other than :normal, all linked processes 
+    # receive an EXIT signal, causing the linked process to 
+    # also terminate unless it is trapping exits.
+    Agent.stop(bucket, :shutdown)
+
+    # Do a call to ensure the registry processed the DOWN message
+    _ = KV.Registry.create(registry, "bogus")
+    assert KV.Registry.lookup(registry, "shopping") == :error
+  end
+end

kv/test/test_helper.exs

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

kv_umbrella/.formatter.exs

@@ -0,0 +1,5 @@
+# Used by "mix format"
+[
+  inputs: ["mix.exs", "config/*.exs"],
+  subdirectories: ["apps/*"]
+]

kv_umbrella/.gitignore

@@ -0,0 +1,20 @@
+# 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 third-party dependencies like ExDoc output generated docs.
+/doc/
+
+# 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
+
+# Temporary files, for example, from tests.
+/tmp/

kv_umbrella/README.md

@@ -0,0 +1,4 @@
+# KvUmbrella
+
+**TODO: Add description**
+

kv_umbrella/apps/kv/.formatter.exs

@@ -0,0 +1,4 @@
+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

kv_umbrella/apps/kv/.gitignore

@@ -0,0 +1,26 @@
+# 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 third-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").
+kv-*.tar
+
+# Temporary files, for example, from tests.
+/tmp/

kv_umbrella/apps/kv/README.md

@@ -0,0 +1,21 @@
+# KV
+
+**TODO: Add description**
+
+## Installation
+
+If [available in Hex](https://hex.pm/docs/publish), the package can be installed
+by adding `kv` to your list of dependencies in `mix.exs`:
+
+```elixir
+def deps do
+  [
+    {:kv, "~> 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/kv>.
+

kv_umbrella/apps/kv/lib/kv.ex

@@ -0,0 +1,10 @@
+defmodule KV do
+  use Application
+
+  @impl true
+  def start(_type, _args) do
+    # Anche se non usiamo KV.Supervisor name direttamente,
+    # e' comodo per debug
+    KV.Supervisor.start_link(name: KV.Supervisor)
+  end
+end

kv_umbrella/apps/kv/lib/kv/bucket.ex

@@ -0,0 +1,33 @@
+defmodule KV.Bucket do
+  use Agent, restart: :temporary
+
+  @doc """
+  Starts a new bucket.
+  """
+  def start_link(_opts) do
+    Agent.start_link(fn -> %{} end)
+  end
+
+  @doc """
+  Gets a value from the `bucket` by `key`.
+  """
+  def get(bucket, key) do
+    Agent.get(bucket, &Map.get(&1, key))
+  end
+
+  @doc """
+  Puts the `value` for the given `key` in the `bucket`.
+  """
+  def put(bucket, key, value) do
+    Agent.update(bucket, &Map.put(&1, key, value))
+  end
+
+  @doc """
+  Deletes `key` from `bucket`.
+
+  Returns the current value of `key`, if `key` exists.
+  """
+  def delete(bucket, key) do
+    Agent.get_and_update(bucket, &Map.pop(&1, key))
+  end
+end

kv_umbrella/apps/kv/lib/kv/registry.ex

@@ -0,0 +1,69 @@
+defmodule KV.Registry do
+  use GenServer
+
+  # Client API
+  @doc """
+  Starts the registry.
+  """
+  def start_link(opts) do
+    server = Keyword.fetch!(opts, :name)
+    GenServer.start_link(__MODULE__, server, opts)
+  end
+
+  @doc """
+  Looks up the bucket pid for `name` stored in `server`.
+
+  Returns `{:ok, pid}` if the bucket exists, `:error` otherwise.
+  """
+  def lookup(server, name) do
+    case :ets.lookup(server, name) do
+      [{^name, pid}] -> {:ok, pid}
+      [] -> :error
+    end
+  end
+
+  @doc """
+  Ensures there is a bucket associated with the given `name` in `server`.
+  """
+  def create(server, name) do
+    GenServer.call(server, {:create, name})
+  end
+
+  # Server Callbacks
+
+  @impl true
+  def init(table) do
+    # name -> bucket
+    names = :ets.new(table, [:named_table, read_concurrency: true])
+    refs = %{} # ref -> name
+    {:ok, {names, refs}}
+  end
+
+  @impl true
+  def handle_call({:create, name}, _from, {names, refs}) do
+    case lookup(names, name) do
+      {:ok, bucket} ->
+        {:reply, bucket, {names, refs}}
+      :error ->
+        {:ok, bucket} = DynamicSupervisor.start_child(KV.BucketSupervisor, KV.Bucket)
+        ref = Process.monitor(bucket)
+        refs = Map.put(refs, ref, name)
+        :ets.insert(names, {name, bucket})
+        {:reply, bucket, {names, refs}}
+    end
+  end
+
+  @impl true
+  def handle_info({:DOWN, ref, :process, _pid, _reason}, {names, refs}) do
+    {name, refs} = Map.pop(refs, ref)
+    :ets.delete(names, name)
+    {:noreply, {names, refs}}
+  end
+
+  @impl true
+  def handle_info(msg, state) do
+    require Logger
+    Logger.debug("Unexpected message in KV.Registry: #{inspect(msg)}")
+    {:noreply, state}
+  end
+end

kv_umbrella/apps/kv/lib/kv/supervisor.ex

@@ -0,0 +1,17 @@
+defmodule KV.Supervisor do
+  use Supervisor
+
+  def start_link(opts) do
+    Supervisor.start_link(__MODULE__, :ok, opts)
+  end
+
+  @impl true
+  def init(:ok) do
+    children = [
+      {DynamicSupervisor, name: KV.BucketSupervisor, strategy: :one_for_one},
+      {KV.Registry, name: KV.Registry},
+    ]
+
+    Supervisor.init(children, strategy: :one_for_all)
+  end
+end

kv_umbrella/apps/kv/mix.exs

@@ -0,0 +1,33 @@
+defmodule KV.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :kv,
+      version: "0.1.0",
+      build_path: "../../_build",
+      config_path: "../../config/config.exs",
+      deps_path: "../../deps",
+      lockfile: "../../mix.lock",
+      elixir: "~> 1.17",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger],
+      mod: {KV, []}
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      # {:dep_from_hexpm, "~> 0.3.0"},
+      # {:dep_from_git, git: "https://github.com/elixir-lang/my_dep.git", tag: "0.1.0"}
+    ]
+  end
+end

kv_umbrella/apps/kv/test/kv/bucket_test.exs

@@ -0,0 +1,15 @@
+defmodule KV.BucketTest do
+  use ExUnit.Case, async: true
+
+  setup do
+    bucket = start_supervised!(KV.Bucket)
+    %{bucket: bucket}
+  end
+
+  test "stores values by key", %{bucket: bucket} do
+    assert KV.Bucket.get(bucket, "milk") == nil
+
+    KV.Bucket.put(bucket, "milk", 3)
+    assert KV.Bucket.get(bucket, "milk") == 3
+  end
+end

kv_umbrella/apps/kv/test/kv/registry_test.exs

@@ -0,0 +1,42 @@
+defmodule KV.RegistryTest do
+  use ExUnit.Case, async: true
+
+  setup context do
+    _ = start_supervised!({KV.Registry, name: context.test})
+    %{registry: context.test}
+  end
+
+  test "spawns buckets", %{registry: registry} do
+    assert KV.Registry.lookup(registry, "shopping") == :error
+
+    KV.Registry.create(registry, "shopping")
+    assert {:ok, bucket} = KV.Registry.lookup(registry, "shopping")
+
+    KV.Bucket.put(bucket, "milk", 1)
+    assert KV.Bucket.get(bucket, "milk") == 1
+  end
+
+  test "removes buckets on exit", %{registry: registry} do
+    KV.Registry.create(registry, "shopping")
+    {:ok, bucket} = KV.Registry.lookup(registry, "shopping")
+    Agent.stop(bucket)
+    # Do a call to ensure the registry processed the DOWN message
+    _ = KV.Registry.create(registry, "bogus")
+    assert KV.Registry.lookup(registry, "shopping") == :error
+  end
+
+  test "removes bucket on crash", %{registry: registry} do
+    KV.Registry.create(registry, "shopping")
+    {:ok, bucket} = KV.Registry.lookup(registry, "shopping")
+
+    # Stop the bucket with non-normal reason
+    # If a process terminates with a reason other than :normal, all linked processes 
+    # receive an EXIT signal, causing the linked process to 
+    # also terminate unless it is trapping exits.
+    Agent.stop(bucket, :shutdown)
+
+    # Do a call to ensure the registry processed the DOWN message
+    _ = KV.Registry.create(registry, "bogus")
+    assert KV.Registry.lookup(registry, "shopping") == :error
+  end
+end

kv_umbrella/apps/kv/test/test_helper.exs

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

kv_umbrella/apps/kv_server/.formatter.exs

@@ -0,0 +1,4 @@
+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

kv_umbrella/apps/kv_server/.gitignore

@@ -0,0 +1,23 @@
+# 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 third-party dependencies like ExDoc output generated docs.
+/doc/
+
+# 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").
+kv_server-*.tar
+
+# Temporary files, for example, from tests.
+/tmp/

kv_umbrella/apps/kv_server/README.md

@@ -0,0 +1,21 @@
+# KVServer
+
+**TODO: Add description**
+
+## Installation
+
+If [available in Hex](https://hex.pm/docs/publish), the package can be installed
+by adding `kv_server` to your list of dependencies in `mix.exs`:
+
+```elixir
+def deps do
+  [
+    {:kv_server, "~> 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/kv_server>.
+

kv_umbrella/apps/kv_server/lib/kv_server.ex

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+defmodule KVServer do
+  @moduledoc """
+  Documentation for `KVServer`.
+  """
+
+  @doc """
+  Hello world.
+
+  ## Examples
+
+      iex> KVServer.hello()
+      :world
+
+  """
+  def hello do
+    :world
+  end
+end

kv_umbrella/apps/kv_server/lib/kv_server/application.ex

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+defmodule KVServer.Application do
+  # See https://hexdocs.pm/elixir/Application.html
+  # for more information on OTP Applications
+  @moduledoc false
+
+  use Application
+
+  @impl true
+  def start(_type, _args) do
+    children = [
+      # Starts a worker by calling: KVServer.Worker.start_link(arg)
+      # {KVServer.Worker, arg}
+    ]
+
+    # See https://hexdocs.pm/elixir/Supervisor.html
+    # for other strategies and supported options
+    opts = [strategy: :one_for_one, name: KVServer.Supervisor]
+    Supervisor.start_link(children, opts)
+  end
+end

kv_umbrella/apps/kv_server/mix.exs

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+defmodule KVServer.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :kv_server,
+      version: "0.1.0",
+      build_path: "../../_build",
+      config_path: "../../config/config.exs",
+      deps_path: "../../deps",
+      lockfile: "../../mix.lock",
+      elixir: "~> 1.18",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger],
+      mod: {KVServer.Application, []}
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      {:kv, in_umbrella: true},
+      # {:dep_from_hexpm, "~> 0.3.0"},
+      # {:dep_from_git, git: "https://github.com/elixir-lang/my_dep.git", tag: "0.1.0"},
+      # {:sibling_app_in_umbrella, in_umbrella: true}
+    ]
+  end
+end

kv_umbrella/apps/kv_server/test/kv_server_test.exs

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+defmodule KVServerTest do
+  use ExUnit.Case
+  doctest KVServer
+
+  test "greets the world" do
+    assert KVServer.hello() == :world
+  end
+end

kv_umbrella/apps/kv_server/test/test_helper.exs

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+ExUnit.start()

kv_umbrella/config/config.exs

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+# This file is responsible for configuring your umbrella
+# and **all applications** and their dependencies with the
+# help of the Config module.
+#
+# Note that all applications in your umbrella share the
+# same configuration and dependencies, which is why they
+# all use the same configuration file. If you want different
+# configurations or dependencies per app, it is best to
+# move said applications out of the umbrella.
+import Config
+
+# Sample configuration:
+#
+#     config :logger, :console,
+#       level: :info,
+#       format: "$date $time [$level] $metadata$message\n",
+#       metadata: [:user_id]
+#

kv_umbrella/mix.exs

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+defmodule KvUmbrella.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      apps_path: "apps",
+      version: "0.1.0",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Dependencies listed here are available only for this
+  # project and cannot be accessed from applications inside
+  # the apps folder.
+  #
+  # Run "mix help deps" for examples and options.
+  defp deps do
+    []
+  end
+end

macros.exs

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+defmodule Unless do
+  def fun_unless(clause, do: expression) do
+    if !clause, do: expression
+  end
+  defmacro macro_unless(clause, do: expression) do
+    quote do 
+      if !unquote(clause), do: unquote(expression)
+    end
+  end
+end

math.exs

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+defmodule Math do
+  def sum(a, b) do
+    a + b
+  end
+end
+
+IO.puts Math.sum(1, 2)