Moar Elixir (Official "Getting Started" Guide)

[nelsonic]

https://elixir-lang.org/getting-started/introduction.html

https://elixir-lang.org/getting-started/introduction.html#interactive-mode

https://elixir-lang.org/getting-started/introduction.html#running-scripts

https://elixir-lang.org/getting-started/basic-types.html

https://elixir-lang.org/getting-started/basic-types.html#basic-arithmetic

https://elixir-lang.org/getting-started/basic-types.html#booleans

https://elixir-lang.org/getting-started/basic-types.html#atoms Took a detour to read: https://www.quora.com/What-are-atoms-in-Erlang-programming-language but got sucked into reading: https://www.quora.com/What-is-something-that-needs-to-be-said (don't fall into the same trap! you will waste a whole pomodoro before you realise it...!)

https://elixir-lang.org/getting-started/basic-types.html#strings

byte_size vs. String.length:

https://elixir-lang.org/getting-started/basic-types.html#anonymous-functions

https://elixir-lang.org/getting-started/basic-types.html#linked-lists

https://elixir-lang.org/getting-started/basic-types.html#tuples

https://elixir-lang.org/getting-started/basic-types.html#lists-or-tuples

Tuples as return values from built-in functions:

good insight at the end of this "chapter" about size vs length operations. size (_e.g: byte_size/1 and tuple_size/1 are pre-computed values and are thus "cheap" operations_) whereas length has a linear (proportional to the length of the list/string etc.) time because String.length/1 needs to "traverse" the entire string to determine it's length. 👍

[nelsonic]

https://elixir-lang.org/getting-started/basic-operators.html

Elixir sorting order (data types):

number < atom < reference < function < port < pid < tuple < map < list < bitstring

[nelsonic]

https://elixir-lang.org/getting-started/pattern-matching.html

https://elixir-lang.org/getting-started/pattern-matching.html#pattern-matching-1

https://elixir-lang.org/getting-started/pattern-matching.html#the-pin-operator

No function calls on the left-hand side of a pattern matching statement:

[nelsonic]

https://elixir-lang.org/getting-started/case-cond-and-if.html https://elixir-lang.org/getting-started/case-cond-and-if.html#cond

https://elixir-lang.org/getting-started/case-cond-and-if.html#if-and-unless

https://elixir-lang.org/getting-started/case-cond-and-if.html#doend-blocks

https://elixir-lang.org/getting-started/binaries-strings-and-char-lists.html

https://elixir-lang.org/getting-started/binaries-strings-and-char-lists.html#binaries-and-bitstrings

https://elixir-lang.org/getting-started/binaries-strings-and-char-lists.html#char-lists

[nelsonic]

https://elixir-lang.org/getting-started/keywords-and-maps.html

https://elixir-lang.org/getting-started/keywords-and-maps.html#maps Map update syntax only for existing keys:

Accessing (atom) keys using dot notation:

https://elixir-lang.org/getting-started/keywords-and-maps.html#nested-data-structures

nested map put_in update syntax:

[nelsonic]

https://elixir-lang.org/getting-started/modules-and-functions.html

https://elixir-lang.org/getting-started/modules-and-functions.html#compilation

https://elixir-lang.org/getting-started/modules-and-functions.html#scripted-mode

https://elixir-lang.org/getting-started/modules-and-functions.html#named-functions

Using do: syntax: You may use do: for one-liners but always use do/end for functions spanning multiple lines.

https://elixir-lang.org/getting-started/modules-and-functions.html#function-capturing

https://elixir-lang.org/getting-started/modules-and-functions.html#default-arguments

Any expression is allowed to serve as a default value, but it won’t be evaluated during the function definition. Every time the function is invoked and any of its default values have to be used, the expression for that default value will be evaluated:

Concat with various clauses:

Second Clause unreachable because first clause Always matches:

[nelsonic]

https://elixir-lang.org/getting-started/recursion.html https://elixir-lang.org/getting-started/recursion.html#loops-through-recursion

https://elixir-lang.org/getting-started/recursion.html#reduce-and-map-algorithms

Inline each clause:

Math.double_each:

Enum.map & Enum.reduce:

[nelsonic]

https://elixir-lang.org/getting-started/enumerables-and-streams.html

https://elixir-lang.org/getting-started/enumerables-and-streams.html#enumerables

https://elixir-lang.org/getting-started/enumerables-and-streams.html#eager-vs-lazy

https://elixir-lang.org/getting-started/enumerables-and-streams.html#the-pipe-operator

https://elixir-lang.org/getting-started/enumerables-and-streams.html#streams "Streams are lazy, composable enumerables."

More stream goodness:

[nelsonic]

https://elixir-lang.org/getting-started/processes.html

https://elixir-lang.org/getting-started/processes.html#spawn

https://elixir-lang.org/getting-started/processes.html#send-and-receive

https://elixir-lang.org/getting-started/processes.html#links

https://elixir-lang.org/getting-started/processes.html#tasks

https://elixir-lang.org/getting-started/processes.html#state

Using Agent for maintaining state:

[nelsonic]

https://elixir-lang.org/getting-started/io-and-the-file-system.html

https://elixir-lang.org/getting-started/io-and-the-file-system.html#the-io-module

https://elixir-lang.org/getting-started/io-and-the-file-system.html#the-file-module

https://elixir-lang.org/getting-started/io-and-the-file-system.html#the-path-module

https://elixir-lang.org/getting-started/io-and-the-file-system.html#processes-and-group-leaders

Of all IO devices, there is one that is special to each process: the group leader ...

https://elixir-lang.org/getting-started/io-and-the-file-system.html#iodata-and-chardata

[nelsonic]

https://elixir-lang.org/getting-started/alias-require-and-import.html

https://elixir-lang.org/getting-started/alias-require-and-import.html#alias

https://elixir-lang.org/getting-started/alias-require-and-import.html#require

https://elixir-lang.org/getting-started/alias-require-and-import.html#import

https://elixir-lang.org/getting-started/alias-require-and-import.html#use

https://elixir-lang.org/getting-started/alias-require-and-import.html#understanding-aliases

https://elixir-lang.org/getting-started/alias-require-and-import.html#module-nesting

https://elixir-lang.org/getting-started/alias-require-and-import.html#multi-aliasimportrequireuse

[nelsonic]

https://elixir-lang.org/getting-started/module-attributes.html

https://elixir-lang.org/getting-started/module-attributes.html#as-annotations

https://elixir-lang.org/getting-started/module-attributes.html#as-constants

https://elixir-lang.org/getting-started/module-attributes.html#as-temporary-storage

[nelsonic]

https://elixir-lang.org/getting-started/structs.html

https://elixir-lang.org/getting-started/structs.html#defining-structs

https://elixir-lang.org/getting-started/structs.html#accessing-and-updating-structs

https://elixir-lang.org/getting-started/structs.html#structs-are-bare-maps-underneath

https://elixir-lang.org/getting-started/structs.html#default-values-and-required-keys

[nelsonic]

https://elixir-lang.org/getting-started/protocols.html

Passing a data type that doesn’t implement the protocol raises an error:

https://elixir-lang.org/getting-started/protocols.html#protocols-and-structs

Implement Size.size for a Struct:

https://elixir-lang.org/getting-started/protocols.html#implementing-any

Note: we set it to 0 (zero) in the implementation...)

https://elixir-lang.org/getting-started/protocols.html#fallback-to-any

https://elixir-lang.org/getting-started/protocols.html#built-in-protocols

https://elixir-lang.org/getting-started/protocols.html#protocol-consolidation

[nelsonic]

https://elixir-lang.org/getting-started/comprehensions.html

https://elixir-lang.org/getting-started/comprehensions.html#generators-and-filters

Show size of each image in "Pictures" directory:

dirs = ['/Users/Admin/Pictures']
for dir  <- dirs,
    file <- File.ls!(dir),
    path = Path.join(dir, file),
    File.regular?(path) do
      IO.puts File.stat!(path).size
end

Simplification:

https://elixir-lang.org/getting-started/comprehensions.html#bitstring-generators

https://elixir-lang.org/getting-started/comprehensions.html#the-into-option

[nelsonic]

https://elixir-lang.org/getting-started/sigils.html

https://elixir-lang.org/getting-started/sigils.html#regular-expressions

https://elixir-lang.org/getting-started/sigils.html#strings-char-lists-and-word-lists-sigils

https://elixir-lang.org/getting-started/sigils.html#interpolation-and-escaping-in-sigils

Heredoc sigils:

https://elixir-lang.org/getting-started/sigils.html#custom-sigils

[nelsonic]

https://elixir-lang.org/getting-started/try-catch-and-rescue.html

https://elixir-lang.org/getting-started/try-catch-and-rescue.html#errors

https://elixir-lang.org/getting-started/try-catch-and-rescue.html#throws

https://elixir-lang.org/getting-started/try-catch-and-rescue.html#exits

https://elixir-lang.org/getting-started/try-catch-and-rescue.html#after

https://elixir-lang.org/getting-started/try-catch-and-rescue.html#else

https://elixir-lang.org/getting-started/try-catch-and-rescue.html#variables-scope

[nelsonic]

https://elixir-lang.org/getting-started/typespecs-and-behaviours.html

https://elixir-lang.org/getting-started/typespecs-and-behaviours.html#defining-custom-types

custom @type is available outside the module definition, to make it private use @typep:

https://elixir-lang.org/getting-started/typespecs-and-behaviours.html#behaviours

https://elixir-lang.org/getting-started/typespecs-and-behaviours.html#defining-behaviours

https://elixir-lang.org/getting-started/typespecs-and-behaviours.html#adopting-behaviours

Ok. I get this. I'll need to use it in a project to remember it tho... 😉

[nelsonic]

https://elixir-lang.org/getting-started/erlang-libraries.html

https://elixir-lang.org/getting-started/erlang-libraries.html#the-binary-module

https://elixir-lang.org/getting-started/erlang-libraries.html#formatted-text-output

https://elixir-lang.org/getting-started/erlang-libraries.html#the-crypto-module

https://elixir-lang.org/getting-started/erlang-libraries.html#the-digraph-module

https://elixir-lang.org/getting-started/erlang-libraries.html#erlang-term-storage

https://elixir-lang.org/getting-started/erlang-libraries.html#the-math-module

https://elixir-lang.org/getting-started/erlang-libraries.html#the-queue-module

https://elixir-lang.org/getting-started/erlang-libraries.html#the-rand-module

https://elixir-lang.org/getting-started/erlang-libraries.html#the-zip-and-zlib-modules didn't work, but when I zipped the contents of the CWD as file.zip:

zip -r ../file.zip ./*

got: and finally:

[nelsonic]

https://elixir-lang.org/getting-started/where-to-go-next.html

[nelsonic]

https://elixir-lang.org/learning.html

[nelsonic]

https://elixir-lang.org/crash-course.html

https://elixir-lang.org/crash-course.html#running-code

https://elixir-lang.org/crash-course.html#elixir

https://elixir-lang.org/crash-course.html#notable-differences

https://elixir-lang.org/crash-course.html#variable-names

https://elixir-lang.org/crash-course.html#calling-functions

https://elixir-lang.org/crash-course.html#data-types

https://elixir-lang.org/crash-course.html#tuples

https://elixir-lang.org/crash-course.html#lists-and-binaries

https://elixir-lang.org/crash-course.html#keyword-list

https://elixir-lang.org/crash-course.html#maps

https://elixir-lang.org/crash-course.html#regular-expressions

https://elixir-lang.org/crash-course.html#modules

https://elixir-lang.org/crash-course.html#function-syntax

see: http://learnyousomeerlang.com/syntax-in-functions

https://elixir-lang.org/crash-course.html#identifying-functions

https://elixir-lang.org/crash-course.html#default-values

https://elixir-lang.org/crash-course.html#anonymous-functions

I prefer the Erlang syntax for anon functions...

https://elixir-lang.org/crash-course.html#first-class-functions

https://elixir-lang.org/crash-course.html#partials-and-function-captures-in-elixir

https://elixir-lang.org/crash-course.html#control-flow

https://elixir-lang.org/crash-course.html#if

https://elixir-lang.org/crash-course.html#sending-and-receiving-messages

https://elixir-lang.org/crash-course.html#adding-elixir-to-existing-erlang-programs

Done. ✅

[nelsonic]

https://elixir-lang.org/getting-started/mix-otp/introduction-to-mix.html

https://elixir-lang.org/getting-started/mix-otp/introduction-to-mix.html#our-first-project

https://elixir-lang.org/getting-started/mix-otp/introduction-to-mix.html#project-compilation

https://elixir-lang.org/getting-started/mix-otp/introduction-to-mix.html#running-tests

(deliberately) Make tests fail:

https://elixir-lang.org/getting-started/mix-otp/introduction-to-mix.html#environments

https://elixir-lang.org/getting-started/mix-otp/introduction-to-mix.html#exploring

[nelsonic]

https://elixir-lang.org/getting-started/mix-otp/agent.html

https://elixir-lang.org/getting-started/mix-otp/agent.html#the-trouble-with-state

https://elixir-lang.org/getting-started/mix-otp/agent.html#agents

Tests first:

Test fails (functionality not yet implemented):

Tests pass:

https://elixir-lang.org/getting-started/mix-otp/agent.html#test-setup-with-exunit-callbacks

using test context with %{bucket: bucket}

https://elixir-lang.org/getting-started/mix-otp/agent.html#other-agent-actions

Delete key TEST First:

delete implemented (test passing):

https://elixir-lang.org/getting-started/mix-otp/agent.html#clientserver-in-agents

(just info. no code to write...)

[nelsonic]

https://elixir-lang.org/getting-started/mix-otp/genserver.html

Never convert user input into atoms as this can exhaust system memory ... 😞

https://elixir-lang.org/getting-started/mix-otp/genserver.html#our-first-genserver

https://elixir-lang.org/getting-started/mix-otp/genserver.html#testing-a-genserver

https://elixir-lang.org/getting-started/mix-otp/genserver.html#the-need-for-monitoring

https://elixir-lang.org/getting-started/mix-otp/genserver.html#call-cast-or-info Just reading. no code.

https://elixir-lang.org/getting-started/mix-otp/genserver.html#monitors-or-links

Onto the next one. 👍

[nelsonic]

https://elixir-lang.org/getting-started/mix-otp/supervisor-and-application.html

https://elixir-lang.org/getting-started/mix-otp/supervisor-and-application.html#our-first-supervisor

https://elixir-lang.org/getting-started/mix-otp/supervisor-and-application.html#naming-processes

https://elixir-lang.org/getting-started/mix-otp/supervisor-and-application.html#understanding-applications

https://elixir-lang.org/getting-started/mix-otp/supervisor-and-application.html#starting-applications

https://elixir-lang.org/getting-started/mix-otp/supervisor-and-application.html#the-application-callback

https://elixir-lang.org/getting-started/mix-otp/supervisor-and-application.html#projects-or-applications

https://elixir-lang.org/getting-started/mix-otp/supervisor-and-application.html#simple-one-for-one-supervisors

Failing Test:

BEFORE:

  def handle_cast({:create, name}, {names, refs}) do
    if Map.has_key?(names, name) do
      {:noreply, {names, refs}}
    else
      {:ok, pid} = KV.Bucket.start_link([])
      ref = Process.monitor(pid)
      refs = Map.put(refs, ref, name)
      names = Map.put(names, name, pid)
      {:noreply, {names, refs}}
    end
  end

AFTER:

  def handle_cast({:create, name}, {names, refs}) do
    if Map.has_key?(names, name) do
      {:noreply, {names, refs}}
    else
      {:ok, pid} = KV.BucketSupervisor.start_bucket()
      ref = Process.monitor(pid)
      refs = Map.put(refs, ref, name)
      names = Map.put(names, name, pid)
      {:noreply, {names, refs}}
    end
  end

Tests pass:

Temporary:

Test:

https://elixir-lang.org/getting-started/mix-otp/supervisor-and-application.html#supervision-trees

https://elixir-lang.org/getting-started/mix-otp/supervisor-and-application.html#observer

Applications:

create "shopping":

https://elixir-lang.org/getting-started/mix-otp/supervisor-and-application.html#shared-state-in-tests

So far so good ... 👍

[nelsonic]

https://elixir-lang.org/getting-started/mix-otp/supervisor-and-application.html#shared-state-in-tests

https://elixir-lang.org/getting-started/mix-otp/ets.html#ets-as-a-cache

Run tests with --trace: (passing intermittently!!)

One failure:

Add "bogus" bucket: Tests pass as expected.

Conclusion: Use "Registry" module:

see: https://hexdocs.pm/elixir/Registry.html

[nelsonic]

https://elixir-lang.org/getting-started/mix-otp/dependencies-and-umbrella-apps.html

https://elixir-lang.org/getting-started/mix-otp/dependencies-and-umbrella-apps.html#external-dependencies

got:

changed the deps to:

 defp deps do
    [
      {:plug, "~> 1.0"}
    ]
  end

See: https://github.com/elixir-lang/elixir-lang.github.com/issues/1019

https://elixir-lang.org/getting-started/mix-otp/dependencies-and-umbrella-apps.html#internal-dependencies

https://elixir-lang.org/getting-started/mix-otp/dependencies-and-umbrella-apps.html#umbrella-projects

run the tests in the umbrella project:

https://elixir-lang.org/getting-started/mix-otp/dependencies-and-umbrella-apps.html#in-umbrella-dependencies

https://elixir-lang.org/getting-started/mix-otp/dependencies-and-umbrella-apps.html#summing-up

[nelsonic]

https://elixir-lang.org/getting-started/mix-otp/task-and-gen-tcp.html

https://elixir-lang.org/getting-started/mix-otp/task-and-gen-tcp.html#echo-server

explanation of code ...

Telnet session:

https://elixir-lang.org/getting-started/mix-otp/task-and-gen-tcp.html#tasks

apps/kv_server/lib/kv_server/application.ex BEFORE

defmodule KVServer.Application do
  # See https://hexdocs.pm/elixir/Application.html
  # for more information on OTP Applications
  @moduledoc false

  use Application

  def start(_type, _args) do
    # List all child processes to be supervised
    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

AFTER:

defmodule KVServer.Application do
  # See https://hexdocs.pm/elixir/Application.html
  # for more information on OTP Applications
  @moduledoc false

  use Application

  def start(_type, _args) do
    # List all child processes to be supervised
    children = [
      {Task, fn -> KVServer.accept(4040) end}
    ]

    # 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

Dual Telnet Connections:

Doesn't work because we need a new process to respond ...

https://elixir-lang.org/getting-started/mix-otp/task-and-gen-tcp.html#task-supervisor

  :ok = :gen_tcp.controlling_process(client, pid)

run: PORT=4040 mix run --no-halt

[nelsonic]

https://elixir-lang.org/getting-started/mix-otp/docs-tests-and-with.html

https://elixir-lang.org/getting-started/mix-otp/docs-tests-and-with.html#doctests

Failing test:

Make it pass:

https://elixir-lang.org/getting-started/mix-otp/docs-tests-and-with.html#with

Start server, connect using Telnet and issue commands:

Re-write serve to use with:

BEFORE:

  defp serve(socket) do
    msg =
      case read_line(socket) do
        {:ok, data} ->
          case KVServer.Command.parse(data) do
            {:ok, command} ->
              KVServer.Command.run(command)
            {:error, _} = err ->
              err
          end
        {:error, _} = err ->
          err
      end

    write_line(socket, msg)
    serve(socket)
  end

AFTER:

  defp serve(socket) do
    msg =
      with {:ok, data} <- read_line(socket),
           {:ok, command} <- KVServer.Command.parse(data),
           do: KVServer.Command.run(command)

    write_line(socket, msg)
    serve(socket)
  end

https://elixir-lang.org/getting-started/mix-otp/docs-tests-and-with.html#running-commands

Implement integration tests:

This tutorial ends with failing tests ... 😕

[nelsonic]

https://elixir-lang.org/getting-started/mix-otp/distributed-tasks-and-configuration.html

https://elixir-lang.org/getting-started/mix-otp/distributed-tasks-and-configuration.html#our-first-distributed-code

Got error:

Protocol 'inet_tcp': invalid node name:  foo@nelson@local

I suspect it has something to do with the two @ symbols ... 😕 When I tried:

iex --sname foo@localhost

It appears to work:

Second instance of iex:

Spawn process in original instance of iex:

Ping the process:

We are going to use Tasks:

https://elixir-lang.org/getting-started/mix-otp/distributed-tasks-and-configuration.html#asyncawait

https://elixir-lang.org/getting-started/mix-otp/distributed-tasks-and-configuration.html#distributed-tasks

iex --sname foo@computer-name -S mix
iex --sname bar@computer-name -S mix

Fails ...

Tests still fail after following the instructions:

However the ==> kv_server Excluding tags: [distributed: true] is working:

At this point nothing is going to work ...

I think I'm going to have to take a few steps back ...