Deep Dive into Elixir

Doing a deep dive into one of my favourite abstractions in Elixir.

Transcript

1. Deep Dive into Elixir Well really, just one abstraction @jonoyeong | ElixirConf 2020
2. Excited to be here @jonoyeong | ElixirConf 2020
3. Pipe Operator @jonoyeong | ElixirConf 2020
4. @jonoyeong | ElixirConf 2020 Documentation
5. “This operator introduces the expression on the left-hand side as the first argument to the function call on the right-hand side.” @jonoyeong | ElixirConf 2020
6. @jonoyeong | ElixirConf 2020
7. Ruby @jonoyeong | ElixirConf 2020
8. Let’s see it in action @jonoyeong | ElixirConf 2020
9. String.downcase(String.reverse("DLROW OLLEH”)) # "hello world” @jonoyeong | ElixirConf 2020 "DLROW OLLEH" |> String.reverse() |> String.downcase() # "hello world”
10. String.downcase(String.reverse("DLROW OLLEH”)) # "hello world” @jonoyeong | ElixirConf 2020 "DLROW OLLEH" |> String.reverse() |> String.downcase() # "hello world”
11. But how tho? @jonoyeong | ElixirConf 2020
12. Pipeline ??? Nested Function @jonoyeong | ElixirConf 2020
13. How is |> defined? Where does it specify the position of the argument? How does it nest/call functions in the pipeline? @jonoyeong | ElixirConf 2020
14. Going down the rabbit hole @jonoyeong | ElixirConf 2020
15. defmacro left |> right do [{h, _} | t] = Macro.unpipe({:|>, [], [left, right]}) fun = fn {x, pos}, acc -> Macro.pipe(acc, x, pos) end :lists.foldl(fun, h, t) end @jonoyeong | ElixirConf 2020
16. defmacro left |> right do @jonoyeong | ElixirConf 2020
17. defmacro left |> right do @jonoyeong | ElixirConf 2020 defmacro
18. Quotes @jonoyeong | ElixirConf 2020
19. Macros take & return quoted Expressions @jonoyeong | ElixirConf 2020
20. quote do: "hello" # "hello" quote do: :world # :world quote do: 1+1 # {:+, [], [1, 1]} quote do: div(a, b) # {:div, [], [{:a, [], Elixir}, {:b, [], Elixir}]} @jonoyeong | ElixirConf 2020
21. How do we inject code? @jonoyeong | ElixirConf 2020
22. Unquoting @jonoyeong | ElixirConf 2020
23. a = 10 b = 2 quote do div(a,b) end # {:div, [], [{:a, [], Elixir}, {:b, [], Elixir}]} quote do div(unquote(a), unquote(b)) end # {:div, [], [10, 2]} @jonoyeong | ElixirConf 2020 a = 10 b = 2 quote do div(a,b) end # {:div, [], [{:a, [], Elixir}, {:b, [], Elixir}]}
24. a = 10 b = 2 quote do div(a,b) end # {:div, [], [{:a, [], Elixir}, {:b, [], Elixir}]} quote do div(unquote(a), unquote(b)) end # {:div, [], [10, 2]} @jonoyeong | ElixirConf 2020 quote do div(unquote(a), unquote(b)) end # {:div, [], [10, 2]}
25. Evaluating a quote? @jonoyeong | ElixirConf 2020
26. Code.eval_quoted(quote do div(unquote(a), unquote(b)) end) # {5, []} Code.eval_quoted(quote do a=1 end) # {1, [{{:a, Elixir}, 1}]} Code.eval_quoted(quote do div(a, b) end) # ** (CompileError) nofile:1: undefined function a/0 @jonoyeong | ElixirConf 2020 Code.eval_quoted(quote do div(unquote(a), unquote(b)) end) # {5, []} Code.eval_quoted(quote do a=1 end) # {1, [{{:a, Elixir}, 1}]}
27. Code.eval_quoted(quote do div(unquote(a), unquote(b)) end) # {5, []} Code.eval_quoted(quote do a=1 end) # {1, [{{:a, Elixir}, 1}]} Code.eval_quoted(quote do div(a, b) end) # ** (CompileError) nofile:1: undefined function a/0 @jonoyeong | ElixirConf 2020 Code.eval_quoted(quote do div(a, b) end) # ** (CompileError) nofile:1: undefined function a/0
28. The textual representation @jonoyeong | ElixirConf 2020
29. Macro.to_string({:+, [], [1, 1]} # "1 + 1” Macro.to_string(quote do div(unquote(a), unquote(b)) end) # "div(10, 2)" @jonoyeong | ElixirConf 2020
30. Macro Recap @jonoyeong | ElixirConf 2020
31. Macros take quoted expressions @jonoyeong | ElixirConf 2020
32. Macros return quoted expressions @jonoyeong | ElixirConf 2020
33. Macros evaluated during compile time @jonoyeong | ElixirConf 2020
34. @jonoyeong | ElixirConf 2020 defmacro left |> right do
35. "DLROW OLLEH" |> String.reverse() |> String.downcase() # === Left === # {:|>, [], # [ # "DLROW OLLEH", # {{:., [], [{:__aliases__, [], [:String]}, :reverse]}, # [], []} # ]} # === Right === # {{:., [], [{:__aliases__, [], [:String]}, :downcase]}, [], # []} @jonoyeong | ElixirConf 2020
36. quote do: "DLROW OLLEH" |> String.reverse() |> String.downcase() {:|>, [], [ {:|>, [], [ "DLROW OLLEH", {{:., [], [{:__aliases__, [alias: false], [:String]}, :reverse]}, [], []} ]}, {{:., [], [{:__aliases__, [alias: false], [:String]}, :downcase]}, [], []} ]} @jonoyeong | ElixirConf 2020
37. quote do: "DLROW OLLEH" |> String.reverse() |> String.downcase() {:|>, [], [ {:|>, [], [ "DLROW OLLEH", {{:., [], [{:__aliases__, [alias: false], [:String]}, :reverse]}, [], []} ]}, {{:., [], [{:__aliases__, [alias: false], [:String]}, :downcase]}, [], []} ]} @jonoyeong | ElixirConf 2020 {:|>, [], [ "DLROW OLLEH", {{:., [], [{:__aliases__, [alias: false], [:String]}, :reverse]}, [], []} ]},
38. quote do: "DLROW OLLEH" |> String.reverse() |> String.downcase() {:|>, [], [ {:|>, [], [ "DLROW OLLEH", {{:., [], [{:__aliases__, [alias: false], [:String]}, :reverse]}, [], []} ]}, {{:., [], [{:__aliases__, [alias: false], [:String]}, :downcase]}, [], []} ]} @jonoyeong | ElixirConf 2020 {{:., [], [{:__aliases__, [alias: false], [:String]}, :downcase]}, [], []}
39. How is |> defined? Where does it specify the position of the argument? How does it nest/call functions in the pipeline? @jonoyeong | ElixirConf 2020
40. How is |> defined? Where does it specify the position of the argument? How does it nest/call functions in the pipeline? @jonoyeong | ElixirConf 2020 ✅
41. defmacro left |> right do [{h, _} | t] = Macro.unpipe({:|>, [], [left, right]}) fun = fn {x, pos}, acc -> Macro.pipe(acc, x, pos) end :lists.foldl(fun, h, t) end @jonoyeong | ElixirConf 2020 [{h, _} | t] = Macro.unpipe({:|>, [], [left, right]}) fun = fn {x, pos}, acc -> Macro.pipe(acc, x, pos) end :lists.foldl(fun, h, t) end
42. [{h, _} | t] = Macro.unpipe({:|>, [], [left, right]}) @jonoyeong | ElixirConf 2020
43. [{h, _} | t] = Macro.unpipe({:|>, [], [left, right]}) @jonoyeong | ElixirConf 2020 Macro.unpipe({:|>, [], [left, right]})
44. def unpipe(expr) do :lists.reverse(unpipe(expr, [])) end defp unpipe({:|>, _, [left, right]}, acc) do unpipe(right, unpipe(left, acc)) end defp unpipe(other, acc) do [{other, 0} | acc] end @jonoyeong | ElixirConf 2020
45. def unpipe(expr) do :lists.reverse(unpipe(expr, [])) end defp unpipe({:|>, _, [left, right]}, acc) do unpipe(right, unpipe(left, acc)) end defp unpipe(other, acc) do [{other, 0} | acc] end @jonoyeong | ElixirConf 2020 defp unpipe(other, acc) do [{other, 0} | acc] end
46. Macro.unpipe(quote do: 100 |> div(5) |> div(2)) # [{100, 0}, {{:div, [], [5]}, 0}, {{:div, [], [2]}, 0}] @jonoyeong | ElixirConf 2020
47. We don’t know how… Yet! @jonoyeong | ElixirConf 2020
48. How is |> defined? Where does it specify the position of the argument? How does it nest/call functions in the pipeline? @jonoyeong | ElixirConf 2020 ✅
49. How is |> defined? Where does it specify the position of the argument? How does it nest/call functions in the pipeline? @jonoyeong | ElixirConf 2020 ✅ ✅
50. defmacro left |> right do [{h, _} | t] = Macro.unpipe({:|>, [], [left, right]}) fun = fn {x, pos}, acc -> Macro.pipe(acc, x, pos) end :lists.foldl(fun, h, t) end @jonoyeong | ElixirConf 2020 fun = fn {x, pos}, acc -> Macro.pipe(acc, x, pos) end :lists.foldl(fun, h, t) end
51. fun = fn {x, pos}, acc -> Macro.pipe(acc, x, pos) end @jonoyeong | ElixirConf 2020
52. def pipe(expr, {op, line, args} = op_args, integer) when is_list(args) do cond do is_atom(op) and Identifier.unary_op(op) != :error -> raise ArgumentError, "cannot pipe #{to_string(expr)} into #{to_string(op_args)}, " <> "the #{to_string(op)} operator can only take one argument" is_atom(op) and Identifier.binary_op(op) != :error -> raise ArgumentError, "cannot pipe #{to_string(expr)} into #{to_string(op_args)}, " <> "the #{to_string(op)} operator can only take two arguments" true -> {op, line, List.insert_at(args, integer, expr)} end end @jonoyeong | ElixirConf 2020
53. def pipe(expr, {op, line, args} = op_args, integer) when is_list(args) do cond do is_atom(op) and Identifier.unary_op(op) != :error -> raise ArgumentError, "cannot pipe #{to_string(expr)} into #{to_string(op_args)}, " <> "the #{to_string(op)} operator can only take one argument" is_atom(op) and Identifier.binary_op(op) != :error -> raise ArgumentError, "cannot pipe #{to_string(expr)} into #{to_string(op_args)}, " <> "the #{to_string(op)} operator can only take two arguments" true -> {op, line, List.insert_at(args, integer, expr)} end end @jonoyeong | ElixirConf 2020 true -> {op, line, List.insert_at(args, integer, expr)}
54. Macro.pipe(100, {:div, [], [5]}, 0) # {:div, [], [100, 5]} Macro.pipe({:div, [], [100, 5]}, {:div, [], [2]}, 0) # {:div, [], [{:div, [], [100, 5]}, 2]} @jonoyeong | ElixirConf 2020
55. I can feel it in my fingers @jonoyeong | ElixirConf 2020
56. :lists.foldl(fun, h, t) @jonoyeong | ElixirConf 2020
57. Atom? What are you doing here? @jonoyeong | ElixirConf 2020
58. Oh this is Erlang @jonoyeong | ElixirConf 2020
59. def left - right do :erlang.-(left, right) end def flatten(list) do :lists.flatten(list) end def mkdir(path) do :file.make_dir(IO.chardata_to_string(path)) end @jonoyeong | ElixirConf 2020
60. i :lists # Term # :lists # Data type # Atom # Description # Call :lists.module_info() to access metadata. # Raw representation # :"lists" # Reference modules # Module, Atom # Implemented protocols # IEx.Info, Inspect, List.Chars, String.Chars @jonoyeong | ElixirConf 2020
61. i :hello # Term # :hello # Data type # Atom # Reference modules # Atom # Implemented protocols # IEx.Info, Inspect, List.Chars, String.Chars @jonoyeong | ElixirConf 2020
62. Erlang/OTP @jonoyeong | ElixirConf 2020
63. Erlang/OTP @jonoyeong | ElixirConf 2020
64. “[Open Telecom Platform] is a set of Erlang libraries and design principles providing middleware to develop systems” Erlang.com @jonoyeong | ElixirConf 2020
65. @jonoyeong | ElixirConf 2020
66. Let’s get back to it @jonoyeong | ElixirConf 2020
67. foldl(Fun, Acc0, List) -> Acc1 lists:foldl(fun(X, Sum) -> X + Sum end, 0, [1,2,3,4,5]). % 15 @jonoyeong | ElixirConf 2020
68. :lists.foldl(fun, h, t) @jonoyeong | ElixirConf 2020 (fun, h, t)
69. fun = fn {x, pos}, acc -> Macro.pipe(acc, x, pos) end @jonoyeong | ElixirConf 2020
70. [{h, _} | t] = Macro.unpipe({:|>, [], [left, right]}) @jonoyeong | ElixirConf 2020 [{h, _} | t]
71. All together now @jonoyeong | ElixirConf 2020
72. @jonoyeong | ElixirConf 2020 100 |> div(5) |> div(2) # [{100, 0}, {{:div, [], [5]}, 0}, {{:div, [], [2]}, 0}] fun = fn {x, pos}, acc -> Macro.pipe(acc, x, pos) end :lists.foldl(fun, 100, [{{:div, [], [5]}, 0}, {{:div, [], [2]}, 0}]) # {:div, [], [{:div, [], [100, 5]}, 2]} Macro.to_string({:div, [], [{:div, [], [100, 5]}, 2]}) # "div(div(100, 5), 2)"
73. @jonoyeong | ElixirConf 2020 100 |> div(5) |> div(2) # [{100, 0}, {{:div, [], [5]}, 0}, {{:div, [], [2]}, 0}] fun = fn {x, pos}, acc -> Macro.pipe(acc, x, pos) end :lists.foldl(fun, 100, [{{:div, [], [5]}, 0}, {{:div, [], [2]}, 0}]) # {:div, [], [{:div, [], [100, 5]}, 2]} Macro.to_string({:div, [], [{:div, [], [100, 5]}, 2]}) # "div(div(100, 5), 2)"
74. @jonoyeong | ElixirConf 2020 100 |> div(5) |> div(2) # [{100, 0}, {{:div, [], [5]}, 0}, {{:div, [], [2]}, 0}] fun = fn {x, pos}, acc -> Macro.pipe(acc, x, pos) end :lists.foldl(fun, 100, [{{:div, [], [5]}, 0}, {{:div, [], [2]}, 0}]) # {:div, [], [{:div, [], [100, 5]}, 2]} Macro.to_string({:div, [], [{:div, [], [100, 5]}, 2]}) # "div(div(100, 5), 2)"
75. @jonoyeong | ElixirConf 2020 100 |> div(5) |> div(2) # [{100, 0}, {{:div, [], [5]}, 0}, {{:div, [], [2]}, 0}] fun = fn {x, pos}, acc -> Macro.pipe(acc, x, pos) end :lists.foldl(fun, 100, [{{:div, [], [5]}, 0}, {{:div, [], [2]}, 0}]) # {:div, [], [{:div, [], [100, 5]}, 2]} Macro.to_string({:div, [], [{:div, [], [100, 5]}, 2]}) # "div(div(100, 5), 2)"
76. How is |> defined? Where does it specify the position of the argument? How does it nest/call functions in the pipeline? @jonoyeong | ElixirConf 2020 ✅ ✅
77. How is |> defined? Where does it specify the position of the argument? How does it nest/call functions in the pipeline? @jonoyeong | ElixirConf 2020 ✅ ✅ ✅
78. Why did I do this again? @jonoyeong | ElixirConf 2020
79. Get a better understanding @jonoyeong | ElixirConf 2020
80. Dispel the magic @jonoyeong | ElixirConf 2020
81. @jonoyeong | ElixirConf 2020 2 |> Integer.to_string(10, ...) # “1010” defp unpipe(ast, acc, %Macro.Env{line: line, file: file}) do case find_pos(ast) do {:ok, new_ast, pos} -> [{new_ast, pos} | acc] {:error, {:already_found, _, _}} -> raise CompileError, file: file, line: line, description: "Doubled placeholder in #{Macro.to_string(ast)}" end end Magritte.ex defp unpipe(ast, acc, %Macro.Env{line: line, file: file}) do case find_pos(ast) do {:ok, new_ast, pos} -> [{new_ast, pos} | acc] end end 2 |> Integer.to_string(10, ...) # “1010”
82. Scratch that itch @jonoyeong | ElixirConf 2020
83. Thank you! @jonoyeong