《Elixir 101》Hello World

最近開始接觸 Elixir 這門語言，語法風格接近 Ruby。而他有一種動靜皆備的特性，老實說還蠻吸引我的。

因為 Elixir 可以用副檔名來區別是要直譯還是編譯，而它的 Elixir 的檔名主要有三種：.ex .exs .beam

這三種檔名差異，可以直接看官方說明：

In addition to the Elixir file extension .ex, Elixir also supports .exs files for scripting. Elixir treats both files exactly the same way, the only difference is in intention. .ex files are meant to be compiled while .exs files are used for scripting. When executed, both extensions compile and load their modules into memory, although only .ex files write their bytecode to disk in the format of .beam files.

Elixir 對於不管是 ex 或者是 exs 檔案，都會將他們編譯後執行；只是在 ex 檔案，Elixir 會將他們寫成 beam格式的二元組碼到硬碟。

不過就像當初接觸 JavaScript 一樣，開始踩了很多坑，並且 Elixir 中文文件並沒有很多，故且將這個學習過程記錄一下，為這門語言貢獻一絲心力。

而學程式語言免不其然傳統上要由 Hello World開始，所以本篇文章將介紹三種方式的 Elixir Hello Word，分別是直接輸入指令、模組引用以及執行檔案。

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第一種：直接輸入指令

$ iex

Erlang/OTP 21 [erts-10.0.5] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [hipe] [dtrace]



Interactive Elixir (1.7.2) - press Ctrl+C to exit (type h() ENTER for help)

iex(1)> IO.puts("Hello World")

Hello World

:ok

iex(2)>

$ iex

Erlang/OTP 21 [erts-10.0.5] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [hipe] [dtrace]



Interactive Elixir (1.7.2) - press Ctrl+C to exit (type h() ENTER for help)

iex(1)> IO.

ANSI                    Stream                  StreamError

binread/1               binread/2               binstream/2

binwrite/1              binwrite/2              chardata_to_string/1

getn/1                  getn/2                  getn/3

gets/1                  gets/2                  inspect/1

inspect/2               inspect/3               iodata_length/1

iodata_to_binary/1      puts/1                  puts/2

read/1                  read/2                  stream/2

warn/1                  warn/2                  write/1

write/2

iex(1)> IO.

第二種：執行檔案

IO.puts("Hello World")

$ elixir hello.ex

Hello World

第三種：模組引用

$ mix new hello-world

** (Mix) Application name must start with a lowercase ASCII letter, followed by lowercase ASCII letters, numbers, or underscores, got: "hello-world". The application name is inferred from the path, if you'd like to explicitly name the application then use the "--app APP" option



$ mix new helloWorld

** (Mix) Application name must start with a lowercase ASCII letter, followed by lowercase ASCII letters, numbers, or underscores, got: "helloWorld". The application name is inferred from the path, if you'd like to explicitly name the application then use the "--app APP" option

$ mix new hello_world

* creating README.md

* creating .formatter.exs

* creating .gitignore

* creating mix.exs

* creating config

* creating config/config.exs

* creating lib

* creating lib/hello_world.ex

* creating test

* creating test/test_helper.exs

* creating test/hello_world_test.exs



Your Mix project was created successfully.

You can use "mix" to compile it, test it, and more:



    cd hello_world

    mix test



Run "mix help" for more commands.

defmodule HelloWorld do

  @moduledoc """

  Documentation for HelloWorld.

  """



  @doc """

  Hello world.



  ## Examples



      iex> HelloWorld.hello()

      :world



  """

  def hello do

    :world

  end

end

$ cd hello_world

$ iex -S mix

Erlang/OTP 21 [erts-10.0.5] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [hipe] [dtrace]



Compiling 1 file (.ex)

Generated hello_world app

Interactive Elixir (1.7.2) - press Ctrl+C to exit (type h() ENTER for help)

iex(1)>

Compiling 1 file (.ex)

Generated hello_world app

iex(1)> HelloWorld.hello()

:world

iex(2)>