Intro to Elixir macro

1.

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2.

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3.

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4.

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6.

EFGNBDSP defmodule MyLogic do defmacro unless(expr, opts) do quote do
if !unquote(expr), unquote(opts) end end end require MyLogic MyLogic.unless false do IO.puts "It works" end

7.

&MJYJSDPEFUP"45 sum(1, 2, 3) => {:sum, [], [1, 2, 3]}
x => {:x, [], Elixir} %{1 => 2} => {:%{}, [], [{1, 2}]} Foo.run(1, 2) => {{:., [], [{:__aliases__, [alias: false], [:Foo]}, :run]}, [], [1, 2]}

8.

RVPUF quote do defmodule Foo do def foo do 1
end end end {:defmodule, [context: Elixir, import: Kernel], [{:__aliases__, [alias: false], [:Foo]}, [do: {:def, [context: Elixir, import: Kernel], [{:foo, [context: Elixir], Elixir}, [do: 1]]}]]}

9.

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10.

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11.

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12.

MFTTDPEF NPSFFFDUJWF defmodule MyRouter do use Plug.Router plug :match #
middleware plug :dispatch # middleware get "/hello" do # logic for a route send_resp(conn, 200, "world") end end

13.

DPNQVUFBUDPNQJMFUJNF # config.yml web_port: 8080 Config.get(:web_port) => 8080 OPUBHPPEFYBNQMF

14.

(FOFSBUFDPEF iex> String.upcase("Elixir Shànghăi") "ELIXIR SHÀNGHĂI" IUUQTHJUIVCDPNFMJYJSMBOHFMJYJSCMPCNBTUFS MJCFMJYJSVOJDPEFVOJDPEFFY-

15.

)PXJTNBDSPJNQMFNFOUFE JO&MJYJS

16.

$PNQJMJOHPG&MJYJS

17.

"OFYBNQMF defmodule Foo do defmacro add1(x) do quote do x
+ 1 end end end Foo.add1(2)

18.

$PEFUP"45 quote do: Foo.add1(2) => { {:., [], [{:__aliases__, [alias:
false], [:Foo]}, :add1]}, [], [2]}

19.

.BDSPFYQBOTJPO require Foo Macro.expand(quote(do: Foo.add1(2)), __ENV__) => {:+, [context: Foo,
import: Kernel], [{:x, [], Foo}, 1]} quote do: Foo.add1(2) => { {:., [], [{:__aliases__, [alias: false], [:Foo]}, :add1]}, [], [2]}

20.

Macro.to_string({:+, [context: Foo, import: Kernel], [{:x, [], Foo}, 1]}) =>
"x + 1" "45UPDPEF

21.

4PPVSDPEFDIBOHFTBGUFSFYQBOTJPO Foo.add1(2) => x + 1

22.

None

23.

)PXUPVTF

24.

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25.

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26.

6TBHFPGUIFMJC defmodule Door do trans :push, "closed", "opened" trans :pull,
"opened", "closed" end state0 = "closed" state1 = Door.push(state0) # "opened" state2 = Door.pull(state1) # "closed"

27.

5IFFYQBOEFEDPEF defmodule Door do def push("closed") do "opened" end def
pull("opened") do "closed" end end

28.

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29.

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30.

defmodule Door do use FSM trans :push, "closed", "opened" trans
:pull, "opened", "closed" end # expanded => defmodule Door do import FSM.DSL, only: [trans: 3] # ... end

31.

defmodule FSM do defmacro __using__(opts) do quote do import FSM.DSL,
only: [trans: 3] end end end defmodule FSM.DSL do defmacro trans(name, from, to) do # ... end end

32.

*NQMFNFOUUSBOTJO'4.%4- defmacro trans(name, from, to) do quote do def name(from)
do to end end end 5IJTJTXSPOH

33.

(FOFSBUFEDPEFXJMMCF defmodule Door do def name(from) do to end def
name(from) do to end end 5IJTJTXSPOH

34.

VORVPUFUPDPNQVUFFYQSFTTJPO CFGPSFNBDSPFYQBOTJPO defmacro trans(name, from, to) do quote do def
unquote(name)(unquote(from)) do unquote(to) end end end

35.

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36.

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37.

defmodule Door do use FSM trans :push, "closed", "opened" trans
:pull, "opened", "closed" end Door.__events__ # => [:push, :pull]

38.

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39.

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40.

defmodule Door do @before_compile FSM.DSL # ... # expanded def
__events__ do # ... end end

41.

defmodule FSM do defmacro __using__(opts) do quote do @before_compile FSM.DSL
end end end defmodule FSM.DSL do defmacro __before_compile__(env) do quote do def __events__ do # ... end end end end

42.

6TFNPEVMFBUUSJCVUFTUPMJTUFWFOUT defmodule FSM do defmacro __using__(opts) do quote do Module.register_attribute(__MODULE__,
:events, accumulate: true) end end end defmacro trans(name, from, to) do quote do @events unquote(name) # ... end end

43.

BOEEFOF@@FWFOUT@@ CFGPSFDPNQJMJOH defmodule FSM.DSL do defmacro __before_compile__(env) do fields =
Module.get_attribute(env.module, :events) quote do def __events__ do unquote(Enum.reverse(fields)) end end end end

44.

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45.

8IFOUPVTFNBDSP

46.

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47.

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48.

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49.

2"

Intro to Elixir macro

Intro to Elixir macro

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