Erlang/OTP: What's in the box? @ ElixirConf LA 2019

When we are first introduced to Elixir we notice that although it does an excellent job in simplifying and abstracting the thorny parts of the platform, every once in a while we encounter some straight calls to Erlang code. Why do we need them? How do they work? Fear not, for these are in fact the tips of amazing, old, beautiful icebergs.

This talk opens the box of Erlang/OTP and introduces some of the coolest built-in tools and libraries available in a standard Erlang/OTP installation, such as wx, ssh, timer, crypto and digraph. We will go over the most popular ones, without forgetting to stop by the most underground (and often underrated) ones, showing some examples of how they can come in handy in numerous occasions.

1. Erlang What is in the box? /OTP
2. João Britto britto noteu
11. # lib/plug/session/ets.ex def init(opts) do Keyword.fetch!(opts, :table) end def put(_conn, sid, data, table) do :ets.insert(table, {sid, data, now()}) sid end defp now() do :os.timestamp() end
12. # lib/plug/session/ets.ex def init(opts) do Keyword.fetch!(opts, :table) end def put(_conn, sid, data, table) do :ets.insert(table, {sid, data, now()}) sid end defp now() do :os.timestamp() end
13. # lib/plug/session/ets.ex def init(opts) do Keyword.fetch!(opts, :table) end def put(_conn, sid, data, table) do :ets.insert(table, {sid, data, now()}) sid end defp now() do :os.timestamp() end
14. # lib/plug/session/ets.ex def init(opts) do Keyword.fetch!(opts, :table) end def put(_conn, sid, data, table) do :ets.insert(table, {sid, data, now()}) sid end defp now() do :os.timestamp() end
15. # lib/plug/session/ets.ex def init(opts) do Keyword.fetch!(opts, :table) end def put(_conn, sid, data, table) do :ets.insert(table, {sid, data, now()}) sid end defp now() do :os.timestamp() end
18. Erlang What is in the box? /OTP
19. # lib/plug/session/ets.ex def init(opts) do Keyword.fetch!(opts, :table) end def put(_conn, sid, data, table) do :ets.insert(table, {sid, data, now()}) sid end defp now() do :os.timestamp() end
20. # lib/plug/session/ets.ex def init(opts) do Keyword.fetch!(opts, :table) end def put(_conn, sid, data, table) do :ets.insert(table, {sid, data, now()}) sid end defp now() do :os.timestamp() end
21. iex> i :an_atom Term :an_atom Data type Atom Reference modules Atom Implemented protocols IEx.Info, Inspect, String.Chars, List.Chars
22. iex> i :an_atom Term :an_atom Data type Atom Reference modules Atom Implemented protocols IEx.Info, Inspect, String.Chars, List.Chars
23. iex> i :an_atom Term :an_atom Data type Atom Reference modules Atom Implemented protocols IEx.Info, Inspect, String.Chars, List.Chars
24. iex> i AnAtom Term AnAtom Data type Atom Raw representation :"Elixir.AnAtom" Reference modules Atom Implemented protocols IEx.Info, Inspect, String.Chars, List.Chars
25. iex> i AnAtom Term AnAtom Data type Atom Raw representation :"Elixir.AnAtom" Reference modules Atom Implemented protocols IEx.Info, Inspect, String.Chars, List.Chars
26. iex> i AnAtom Term AnAtom Data type Atom Raw representation :"Elixir.AnAtom" Reference modules Atom Implemented protocols IEx.Info, Inspect, String.Chars, List.Chars
27. iex> i AnAtom Term AnAtom Data type Atom Raw representation :"Elixir.AnAtom" Reference modules Atom Implemented protocols IEx.Info, Inspect, String.Chars, List.Chars
28. iex> i Keyword Term Keyword Data type Atom Module bytecode elixir/ebin/Elixir.Keyword.beam Source elixir/lib/keyword.ex Version [18490583473799941736109510131724656698] Compile options [:debug_info] Description Use h(Keyword) to access its documentation. Call Keyword.module_info() to access metadata. Raw representation :"Elixir.Keyword" Reference modules Module, Atom Implemented protocols IEx.Info, Inspect, String.Chars, List.Chars
29. iex> i Keyword Term Keyword Data type Atom Module bytecode elixir/ebin/Elixir.Keyword.beam Source elixir/lib/keyword.ex Version [18490583473799941736109510131724656698] Compile options [:debug_info] Description Use h(Keyword) to access its documentation. Call Keyword.module_info() to access metadata. Raw representation :"Elixir.Keyword" Reference modules Module, Atom Implemented protocols IEx.Info, Inspect, String.Chars, List.Chars
30. iex> i Keyword Term Keyword Data type Atom Module bytecode elixir/ebin/Elixir.Keyword.beam Source elixir/lib/keyword.ex Version [18490583473799941736109510131724656698] Compile options [:debug_info] Description Use h(Keyword) to access its documentation. Call Keyword.module_info() to access metadata. Raw representation :"Elixir.Keyword" Reference modules Module, Atom Implemented protocols IEx.Info, Inspect, String.Chars, List.Chars
31. iex> i Keyword Term Keyword Data type Atom Module bytecode elixir/ebin/Elixir.Keyword.beam Source elixir/lib/keyword.ex Version [18490583473799941736109510131724656698] Compile options [:debug_info] Description Use h(Keyword) to access its documentation. Call Keyword.module_info() to access metadata. Raw representation :"Elixir.Keyword" Reference modules Module, Atom Implemented protocols IEx.Info, Inspect, String.Chars, List.Chars
32. iex> i Keyword Term Keyword Data type Atom Module bytecode elixir/ebin/Elixir.Keyword.beam Source elixir/lib/keyword.ex Version [18490583473799941736109510131724656698] Compile options [:debug_info] Description Use h(Keyword) to access its documentation. Call Keyword.module_info() to access metadata. Raw representation :"Elixir.Keyword" Reference modules Module, Atom Implemented protocols IEx.Info, Inspect, String.Chars, List.Chars
33. iex> i :os Term :os Data type Atom Module bytecode erlang/21.0.4/lib/kernel-6.0/ebin/os.beam Source otp_src_21.0.4/lib/kernel/src/os.erl Version [8891021078382918036082292112481311050] Compile options [:debug_info, {:i, 'otp_src_21.0.4/lib/kernel/src/../include'}] Description Call :os.module_info() to access metadata. Raw representation :"os" Reference modules Module, Atom Implemented protocols IEx.Info, Inspect, String.Chars, List.Chars
34. iex> i :os Term :os Data type Atom Module bytecode erlang/21.0.4/lib/kernel-6.0/ebin/os.beam Source otp_src_21.0.4/lib/kernel/src/os.erl Version [8891021078382918036082292112481311050] Compile options [:debug_info, {:i, 'otp_src_21.0.4/lib/kernel/src/../include'}] Description Call :os.module_info() to access metadata. Raw representation :"os" Reference modules Module, Atom Implemented protocols IEx.Info, Inspect, String.Chars, List.Chars
35. iex> i :os Term :os Data type Atom Module bytecode erlang/21.0.4/lib/kernel-6.0/ebin/os.beam Source otp_src_21.0.4/lib/kernel/src/os.erl Version [8891021078382918036082292112481311050] Compile options [:debug_info, {:i, 'otp_src_21.0.4/lib/kernel/src/../include'}] Description Call :os.module_info() to access metadata. Raw representation :"os" Reference modules Module, Atom Implemented protocols IEx.Info, Inspect, String.Chars, List.Chars
36. iex> i :os Term :os Data type Atom Module bytecode erlang/21.0.4/lib/kernel-6.0/ebin/os.beam Source otp_src_21.0.4/lib/kernel/src/os.erl Version [8891021078382918036082292112481311050] Compile options [:debug_info, {:i, 'otp_src_21.0.4/lib/kernel/src/../include'}] Description Call :os.module_info() to access metadata. Raw representation :"os" Reference modules Module, Atom Implemented protocols IEx.Info, Inspect, String.Chars, List.Chars
37. iex> i :os Term :os Data type Atom Module bytecode erlang/21.0.4/lib/kernel-6.0/ebin/os.beam Source otp_src_21.0.4/lib/kernel/src/os.erl Version [8891021078382918036082292112481311050] Compile options [:debug_info, {:i, 'otp_src_21.0.4/lib/kernel/src/../include'}] Description Call :os.module_info() to access metadata. Raw representation :"os" Reference modules Module, Atom Implemented protocols IEx.Info, Inspect, String.Chars, List.Chars
38. iex> :c c calendar cerl cerl_clauses cerl_inline cerl_sets cerl_trees code code_server compile core_lib core_lint core_parse core_pp core_scan iex> :d dets dets_server dets_sup dets_utils dets_v9 dict digraph digraph_utils disk_log disk_log_1 disk_log_server disk_log_sup dist_ac dist_util iex> :g gb_sets gb_trees gen gen_event gen_fsm gen_sctp gen_server gen_statem gen_tcp gen_udp global global_group global_search group group_history iex> :l lists local_tcp local_udp log_mf_h logger logger_backend logger_config logger_disk_log_h logger_filters logger_formatter logger_h_common logger_server logger_simple_h logger_std_h logger_sup
39. iex> :c c calendar cerl cerl_clauses cerl_inline cerl_sets cerl_trees code code_server compile core_lib core_lint core_parse core_pp core_scan iex> :d dets dets_server dets_sup dets_utils dets_v9 dict digraph digraph_utils disk_log disk_log_1 disk_log_server disk_log_sup dist_ac dist_util iex> :g gb_sets gb_trees gen gen_event gen_fsm gen_sctp gen_server gen_statem gen_tcp gen_udp global global_group global_search group group_history iex> :l lists local_tcp local_udp log_mf_h logger logger_backend logger_config logger_disk_log_h logger_filters logger_formatter logger_h_common logger_server logger_simple_h logger_std_h logger_sup
40. –Elixir Getting Started Guide “Elixir provides excellent interoperability with Erlang libraries. In fact, Elixir discourages simply wrapping Erlang libraries in favor of directly interfacing with Erlang code.”
41. Atoms & Modules • All modules are atoms • But not all atoms are modules • Elixir identifiers are prefixed implicitly • Interoperability between Elixir and Erlang is very seamless
43. –Francesco Cesarini & Steve Vinoski “OTP is a domain-independent set of frameworks, principles, and patterns that guide and support the structure, design, implementation, and deployment of Erlang systems.”
44. Erlang/OTP Language Tools Principles
45. Erlang/OTP • Language: Erlang itself, its programming model and the BEAM. • Tools: all the applications and libraries included. • Design Principles: supervision trees, behaviours, applications and releases.
46. http://erlang.org/doc/applications.html
53. Manual Page Application alarm_handler sasl-3.2 app kernel-6.0 application kernel-6.0 appup sasl-3.2 array stdlib-3.5 asn1ct asn1-5.0.6 assert.hrl stdlib-3.5 auth kernel-6.0 base64 stdlib-3.5 beam_lib stdlib-3.5 binary stdlib-3.5 c stdlib-3.5 calendar stdlib-3.5 cdv observer-2.8 code kernel-6.0 common_test common_test-1.16 compile compiler-7.2 config kernel-6.0 cover tools-3.0 cprof tools-3.0 cpu_sup os_mon-2.4.5 crashdump_viewer observer-2.8 crypto crypto-4.3 crypto_app crypto-4.3 ct common_test-1.16 ct_cover common_test-1.16 ct_ftp common_test-1.16
54. snmpc snmp-5.2.11 snmpc(command) snmp-5.2.11 snmpm snmp-5.2.11 snmpm_conf snmp-5.2.11 snmpm_mpd snmp-5.2.11 snmpm_network_interface snmp-5.2.11 snmpm_network_interface_filter snmp-5.2.11 snmpm_user snmp-5.2.11 sofs stdlib-3.5 ssh ssh-4.7 SSH_app ssh-4.7 ssh_client_channel ssh-4.7 ssh_client_key_api ssh-4.7 ssh_connection ssh-4.7 ssh_server_channel ssh-4.7 ssh_server_key_api ssh-4.7 ssh_sftp ssh-4.7 ssh_sftpd ssh-4.7 ssl ssl-9.0 ssl_app ssl-9.0 ssl_crl_cache ssl-9.0 ssl_crl_cache_api ssl-9.0 ssl_session_cache_api ssl-9.0 start erts-10.0 start_erl erts-10.0 STDLIB_app stdlib-3.5 string stdlib-3.5 supervisor stdlib-3.5 supervisor_bridge stdlib-3.5
55. inets
56. $ cat index.html <html> <body> <h1>Hello!</h1> </body> </html>
57. $ iex --app inets Erlang/OTP 21 [erts-10.0.4] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [hipe] Interactive Elixir (1.7.3) - press Ctrl+C to exit (type h() ENTER for help) iex>
58. $ iex --app inets Erlang/OTP 21 [erts-10.0.4] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [hipe] Interactive Elixir (1.7.3) - press Ctrl+C to exit (type h() ENTER for help) iex> options = [ server_name: 'Elixir Conf 2018', document_root: '.', server_root: '.', port: 8080 ] iex> {:ok, server} = :inets.start(:httpd, options) {:ok, #PID<0.116.0>}
59. iex> :httpd.info(server) [ mime_types: [{'htm', 'text/html'}, {'html', 'text/html'}], ipfamily: :inet, server_name: 'Elixir Conf 2018', bind_address: :any, server_root: '.', port: 8080, document_root: '.' ]
62. iex> :httpc.request('http://localhost:8080/index.html') {:ok, {{'HTTP/1.1', 200, 'OK'}, [ {'date', 'Wed, 05 Sep 2018 05:55:55 GMT'}, {'etag', 'nJCRTD54'}, {'server', 'inets/7.0'}, {'content-length', '54'}, {'content-type', 'text/html'}, {'last-modified', 'Sun, 02 Sep 2018 20:19:03 GMT'} ], '<html>\n <body>\n <h1>Hello!</h1>\n </body>\n</html>\n'}}
63. inets • Not only a fully capable HTTP server, but also client. • It used to manage FTP and T(rivial)FTP clients and servers, but they have been recently split out into their own apps.
64. ssh
65. $ iex --app ssh Erlang/OTP 21 [erts-10.0.4] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [hipe] Interactive Elixir (1.7.2) - press Ctrl+C to exit (type h() ENTER for help) iex> :ok = :ssh.shell('secure.locati.on', user: 'me', password: ‘secret') :ok me@secure.locati.on:> pwd /home/me me@secure.locati.on:> exit logout iex>
66. ssh • Both client and server. • SFTP client and server too. • Basically everything you can do with your unix ssh. • Even tunneling!
67. ssh • Both client and server. • SFTP client and server too. • Basically everything you can do with your unix ssh. • Even tunneling!
68. ets
69. defmodule Plug.Session.ETS do @moduledoc """ Stores the session in an in-memory ETS table. The data is stored in ETS in the following format: {sid :: String.t, data :: map, timestamp :: :erlang.timestamp} The timestamp is updated whenever there is a read or write to the table and it may be used to detect if a session is still active. ## Examples # Create an ETS table when the application starts :ets.new(:session, [:named_table, :public, read_concurrency: true]) # Use the session plug with the table name plug Plug.Session, store: :ets, key: "sid", table: :session """ @behaviour Plug.Session.Store def init(opts) do Keyword.fetch!(opts, :table) end end
70. def get(_conn, sid, table) do case :ets.lookup(table, sid) do [{^sid, data, _timestamp}] -> :ets.update_element(table, sid, {3, now()}) {sid, data} [] -> {nil, %{}} end end def put(_conn, sid, data, table) do :ets.insert(table, {sid, data, now()}) sid end def delete(_conn, sid, table) do :ets.delete(table, sid) :ok end defp now, do: :os.timestamp()
71. def get(_conn, sid, table) do case :ets.lookup(table, sid) do [{^sid, data, _timestamp}] -> :ets.update_element(table, sid, {3, now()}) {sid, data} [] -> {nil, %{}} end end def put(_conn, sid, data, table) do :ets.insert(table, {sid, data, now()}) sid end def delete(_conn, sid, table) do :ets.delete(table, sid) :ok end defp now, do: :os.timestamp()
72. def get(_conn, sid, table) do case :ets.lookup(table, sid) do [{^sid, data, _timestamp}] -> :ets.update_element(table, sid, {3, now()}) {sid, data} [] -> {nil, %{}} end end def put(_conn, sid, data, table) do :ets.insert(table, {sid, data, now()}) sid end def delete(_conn, sid, table) do :ets.delete(table, sid) :ok end defp now, do: :os.timestamp()
73. def get(_conn, sid, table) do case :ets.lookup(table, sid) do [{^sid, data, _timestamp}] -> :ets.update_element(table, sid, {3, now()}) {sid, data} [] -> {nil, %{}} end end def put(_conn, sid, data, table) do :ets.insert(table, {sid, data, now()}) sid end def delete(_conn, sid, table) do :ets.delete(table, sid) :ok end defp now, do: :os.timestamp()
74. crypto
75. @max_tries 100 def put(_conn, nil, data, table) do put_new(data, table) end def put(_conn, sid, data, table) do :ets.insert(table, {sid, data, now()}) sid end defp put_new(data, table, counter \\ 0) when counter < @max_tries do sid = Base.encode64(:crypto.strong_rand_bytes(96)) if :ets.insert_new(table, {sid, data, now()}) do sid else put_new(data, table, counter + 1) end end defp now, do: :os.timestamp()
76. @max_tries 100 def put(_conn, nil, data, table) do put_new(data, table) end def put(_conn, sid, data, table) do :ets.insert(table, {sid, data, now()}) sid end defp put_new(data, table, counter \\ 0) when counter < @max_tries do sid = Base.encode64(:crypto.strong_rand_bytes(96)) if :ets.insert_new(table, {sid, data, now()}) do sid else put_new(data, table, counter + 1) end end defp now, do: :os.timestamp()
77. @max_tries 100 def put(_conn, nil, data, table) do put_new(data, table) end def put(_conn, sid, data, table) do :ets.insert(table, {sid, data, now()}) sid end defp put_new(data, table, counter \\ 0) when counter < @max_tries do sid = Base.encode64(:crypto.strong_rand_bytes(96)) if :ets.insert_new(table, {sid, data, now()}) do sid else put_new(data, table, counter + 1) end end defp now, do: :os.timestamp()
78. @max_tries 100 def put(_conn, nil, data, table) do put_new(data, table) end def put(_conn, sid, data, table) do :ets.insert(table, {sid, data, now()}) sid end defp put_new(data, table, counter \\ 0) when counter < @max_tries do sid = Base.encode64(:crypto.strong_rand_bytes(96)) if :ets.insert_new(table, {sid, data, now()}) do sid else put_new(data, table, counter + 1) end end defp now, do: :os.timestamp()
79. observer
80. :observer.start()
83. et: event trace
85. –Event Tracer User’s Guide “Erlang tracing is a seething pile of pain that involves reasonably complex knowledge of clever ports, tracing return formats, and specialized tracing MatchSpecs (which are really their own special kind of hell). The tracing mechanism is very powerful indeed, but it can be hard to grasp.”
86. :et_viewer.start( trace_global: true, trace_pattern: {:et, :max}, title: "Making Sandwich", width: 500, height: 400 ) sandwich = %{ bread: :white, mayo: true, tomato: false } :et.trace_me(70, :alice, :bob, :make_sandwich, sandwich) :et.trace_me(80, :bob, :fridge, :get_bread, :white) :et.trace_me(80, :fridge, :bob, :give_bread, :white) :et.trace_me(80, :bob, :fridge, :get_spread, :mayo) :et.trace_me(80, :fridge, :bob, :give_spread, :mayo) :et.trace_me(90, :bob, :bob, :assemble_sandwich, [:white_bread, :mayo, :filling]) :et.trace_me(70, :bob, :alice, :sandwich_ready, sandwich)
92. et • Collects and displays events in real-time. • Nice filtering features. • Possibilities seem to be endless: debugging a piece of concurrent code, building simulated scenarios, understanding a new codebase.
93. wx
94. :wx.demo()
96. stdlib
97. binary & string
98. Longest.common_prefix(["erlang", "elixir"]) # 1 Longest.common_prefix(["yodel", "yoda", "yolo"]) # 2 Longest.common_prefix(["yolo"]) # 4
99. defmodule Longest do def common_prefix([]), do: raise(ArgumentError) def common_prefix([word]), do: String.length(word) def common_prefix([word1, word2 | words]) do length1 = common_prefix([word2 | words]) length2 = common_prefix(word1, word2, 0) Enum.min([length1, length2]) end defp common_prefix(<<hd::utf8, a::binary>>, <<hd::utf8, b::binary>>, count) do common_prefix(a, b, count + 1) end defp common_prefix(_, _, count), do: count end
100. defmodule Longest do def common_prefix([]), do: raise(ArgumentError) def common_prefix(words), do: common_prefix(words, 0) defp common_prefix([word | words] = all, position) do common = Enum.reduce_while(words, String.at(word, position), fn current, char -> if char && char == String.at(current, position), do: {:cont, char}, else: {:halt, false} end) if common, do: common_prefix(all, position + 1), else: position end end
101. :binary.longest_common_prefix(["erlang", "elixir"]) # 1 :binary.longest_common_prefix(["yodel", "yoda", "yolo"]) # 2 :binary.longest_common_prefix(["yolo"]) # 4
102. # I want to print this: "elixir" # centered, like this: "--elixir--"
103. "elixir" |> String.pad_leading(8, "-") |> String.pad_trailing(10, "-") |> IO.puts() --elixir--
104. "elixir" |> :string.pad(10, :both, "-") |> IO.puts() --elixir--
105. digraph & digraph_utils
108. –Johan Bevemyr (Cisco Systems) “90% of all internet traffic goes through Erlang controller nodes.”
110. test "convoluted path" do board = remove_spaces([ ". X X . .", " X . X . X", " . X . X .", " . X X . .", " O O O O O" ]) assert Connect.result_for(board) == :black end
111. defp black_wins?(board) do # ... black |> graph() |> connects?(left, right) end defp white_wins?(board) do # ... white |> graph() |> connects?(top, bottom) end
112. defp graph(tiles) do graph = :digraph.new() for tile <- tiles, do: :digraph.add_vertex(graph, tile) for tile <- tiles, do: connect_neighbors(graph, tile) graph end defp connect_neighbors(graph, tile) do for neighbor <- neighbors(tile), :digraph.vertex(graph, neighbor) do :digraph.add_edge(graph, tile, neighbor) :digraph.add_edge(graph, neighbor, tile) end end
113. defp graph(tiles) do graph = :digraph.new() for tile <- tiles, do: :digraph.add_vertex(graph, tile) for tile <- tiles, do: connect_neighbors(graph, tile) graph end defp connect_neighbors(graph, tile) do for neighbor <- neighbors(tile), :digraph.vertex(graph, neighbor) do :digraph.add_edge(graph, tile, neighbor) :digraph.add_edge(graph, neighbor, tile) end end ⚠ Mutability ⚠
114. defp connects?(graph, sources, destinations) do sources |> :digraph_utils.reachable(graph) |> intersect?(destinations) end
115. lists
116. not_flat = [1, [2, 3, [4, [5, 6]], 7], 8]
117. not_flat = [1, [2, 3, [4, [5, 6]], 7], 8] not_flat |> List.flatten() |> length() # 8
118. not_flat = [1, [2, 3, [4, [5, 6]], 7], 8] :lists.flatlength(not_flat) # 8
119. list = [1, 2, 3, 4, 5] {_, body} = List.pop_at(list, -1) body # [1, 2, 3, 4]
120. list = [1, 2, 3, 4, 5] Enum.slice(list, 0..-2) # [1, 2, 3, 4]
121. list = [1, 2, 3, 4, 5] :lists.droplast(list) # [1, 2, 3, 4]
122. timer
123. time_this(fn -> "too fast" end) # {5, "too fast"}
124. def time_this(fun) do start = System.monotonic_time(:microseconds) result = fun.() elapsed = System.monotonic_time(:microseconds) - start; {elapsed, result} end time_this(fn -> "too fast" end) # {5, "too fast"}
125. :timer.tc(fn -> "too fast" end) # {5, "too fast”}
126. three_hours = 3 * 60 * 60 * 1000 # 10_800_000
127. three_hours = :timer.hours(3) # 10_800_000
128. two_and_a_half_hours = 150 * 60 * 1000 # 9_000_000
129. two_and_a_half_hours = :timer.hms(2, 30, 0) # 9_000_000
130. queue
131. iex> q = :queue.new() {[], []} iex> q = :queue.in(:first, q) {[:first], []} iex> q = :queue.in(:second, q) {[:second], [:first]} iex> q = :queue.in(:third, q) {[:third, :second], [:first]} iex> q = :queue.in(:fourth, q) {[:fourth, :third, :second], [:first]} iex> {{:value, first}, q} = :queue.out(q) {{:value, :first}, {[:fourth, :third], [:second]}} iex> first :first iex> q {[:fourth, :third], [:second]}
132. rand
133. iex> :rand.uniform(20) 13 iex> :rand.uniform(30) 25 iex> :rand.uniform(30) 12 iex> :rand.uniform(30) 27 iex> :rand.uniform(30) 10 iex> :rand.uniform(30) 6 iex> :rand.uniform(30) 2 iex> :rand.uniform(30) 20 iex> :rand.uniform(30) 16 iex> :rand.uniform(30) 9 iex> :rand.uniform(30) 28
134. stdlib
135. “If you ever feel something is missing from Elixir standard libraries, it’s for a reason. It’s somewhere else, and that’s by design. So go explore. Don’t stop at Elixir, there’s a lot underneath the surface.”
136. “Share your findings. We’ll all learn faster and better together.”
137. Elixir Brasil 2020 Sponsors are welcome! https://forms.gle/wFVjTXc2zfwoWq4b9 elixir_brasil https://2019.elixirbrasil.com/
138. ¡Gracias!
139. Resources and References • Plug Session ETS adapter • https://github.com/elixir-plug/plug/blob/v1.6.2/lib/plug/session/ets.ex • Open Erlang - celebrating 20 years of open sourced Erlang • https://www.erlang-solutions.com/open-erlang.html • Open-source Erlang - White Paper • https://web.archive.org/web/20150721215830/http://ftp.sunet.se/pub/lang/erlang/white_paper.html • Elixir Getting Started Guides - Erlang Libraries • https://elixir-lang.org/getting-started/erlang-libraries.html • Designing for Scalability with Erlang/OTP: Implementing Robust, Fault-Tolerant Systems • https://www.goodreads.com/book/show/18324312-designing-for-scalability-with-erlang-otp • Erlang Programming • https://www.goodreads.com/book/show/4826120-erlang-programming
140. Resources and References • Erlang/OTP 21.0 official documentation • http://erlang.org/doc/index.html • Learn You Some Erlang for Great Good! • https://learnyousomeerlang.com/ • Implementing SSH tunnels in Elixir • https://medium.com/@Drowzy/implementing-ssh-tunnels-in-elixir-e7ad9d1af01a • Exercism Connect challenge and solution • https://exercism.io/solutions/bb97260806b349c2a14203af56846d7a • Hex (board game) • https://en.wikipedia.org/wiki/Hex_(board_game) • Mix dependencies converger • https://github.com/elixir-lang/elixir/blob/v1.7.3/lib/mix/lib/mix/dep/converger.ex
141. Image Credits • https://unsplash.com/photos/Y3vPEuNlf7w • https://unsplash.com/photos/nCj0zBLIaAk • https://www.adweek.com/agencies/nikes-new-soccer-film-is-a-monster-of-a-tall-tale/ • https://www.reshot.com/photos/red-christmas-ribbon-coffee-cup-cup-box-xmas-present-present-box-christmas-holidays_rs_P3ryYN • https://unsplash.com/photos/MGaFENpDCsw • https://unsplash.com/photos/1YXkcpxu8S8 • https://unsplash.com/photos/uGcDWKN91Fs • https://unsplash.com/photos/JuFcQxgCXwA • https://pixabay.com/en/move-key-new-apartment-catchment-2481718/ • https://www.pexels.com/photo/man-in-grey-dress-shirt-using-brown-cardboard-vr-glasses-936575/ • https://unsplash.com/photos/qWwpHwip31M • https://www.pexels.com/photo/close-up-of-crayons-inside-box-1234937/ • https://unsplash.com/photos/wEJK4q_YlNQ • https://unsplash.com/photos/sxNt9g77PE0