http://oscardelben.com/seven-languages-io-day-1

我刚买了Seven languages in seven weeks这本书的Beta版，真是一本好书。

这本书每章介绍一门编程语言，总共是七门语言。每章你都能找到语言的介绍，还有一些练习和自学题目。实际上每章也分成三天，我将用“第一天”“第二天”“第三天”来写它们。

这本书里介绍了下面这些编程语言：

Ruby

IOLanguage

Prolog

Scala

Erlang

Clujure

Haskell

因为我（原作者）知道ruby了，就很快翻到第二章IOLanguage。IO是一门原型编程语言，某种程度上类似javascript（译者注：类似语言还有Lua）。我喜欢这门语言的语法和简洁性。

在Mac os X上安装IO

如果你想编译所有依赖库，从源代码开始安装需要一些时间。这里我们使用macports来获取所有依赖库，你可以在这里http://www.iolanguage.com/scm/io/docs/IoGuide.html#Introduction-Installing找到详细的安装文档。

1: cd ~/

2: git clone git://github.com/stevedekorte/io.git

3: cd io

4: make vm; sudo make install; sudo make port; sudo make install

你可能不得不加入一些辅助库，可以参考前面关于安装的在线文档知道详细步骤。

如果你想安装textmate的绑定，可以运行以下命令：

1: cd “/Library/Application Support/TextMate/Bundles”

2: svn co http://svn.textmate.org/trunk/Bundles/Io.tmbundle/

就是这些，现在可以运行Terminal程序了。

IO语言基础

IO编程语言的完整介绍可以参考这里http://www.iolanguage.com/scm/io/docs/IoGuide.html

下面是一个简单的预览：

1: Io 20090105

3: Io> 3 * 4

4: ==> 12

6: Io> Animal := Object clone

7: ==> Animal_0x10034c170:

8: type = “Animal”

10:

11: Io> Animal description := “All animals in the world”

12: ==> All animals in the world

13:

14: Io> dog := Animal clone

15: ==> Animal_0x10033f5f0:

16:

17: Io> dog description

18: ==> All animals in the world

19:

20: Io> dog description := “A generic dog”

21: ==> A generic dog

22:

23: Io> dog description

24: ==> A generic dog

25:

26: Io> dog talk := method(“Baw” print)

27: ==> method(

28: “Baw” print

29: )

30:

31: Io> dog talk()

32: Baw==> Baw

33:

34: Io> list(1, 2, 3) sum

35: ==> 6

36:

37: Io> list(1, 2, 3) average

38: ==> 2

39:

40: Io> list(1, 2, 3) map(x, x * x)

41: ==> list(1, 4, 9)

42:

43: Io> fibonacci := method(n, if(n < 2, n, (fibonacci(n -1) + fibonacci(n - 2))))

44: ==> method(n,

45: if(n < 2, n, (fibonacci(n - 1) + fibonacci(n - 2)))

46: )

47: Io> fibonacci(34)

48: ==> 5702887

先别担心这语言看上去有些怪异，实际上你会发现它的语法非常简单。

通过IO建立一个在线新闻程序

这是我做的一个小练习，刚刚学过语言以后，用IO语言在20分钟内创建一个简单版本的新闻平台。代码不是很出彩，但是它证明了使用IO多轻松简单。

1: # INSTANTIATE DB

3: db := SQLite clone

4: db setPath(“news.sqlite”)

6: # HTML HELPERS

8: ul := method(content, "

" .. content .. "")

10: li := method(content, "

".. content .. "

11:

12: a := method(text, url, “<a href=\”#{url}\”>#{text}” interpolate)

13:

14: form := method(action, content, “<form action=\”#{action}\” method=\“get\”>” interpolate .. content .. "")

15:

16: field := method(name, ”#{name}: <input type=\“text\” name=\”#{name}\” \>” interpolate)

17:

18: submit := method(“<input type=\“submit\” />”)

19:

20: with_template := method(title, body,

21: ”<!DOCTYPE HTML PUBLIC \”-//W3C//DTD HTML 4.01 Transitional//EN\”

22: \“http://www.w3.org/TR/html4/loose.dtd\\”>

23:

24:

25: <meta http-equiv=\“Content-type\” content=\“text/html; charset=utf-8\”>

26: ” .. title .. ”

27: <style type=\“text/css\” media=\“screen\”>

28: body {

29: background:#ffffcc;

30: margin:20px;

31: padding:0;

32: font-family:Calibri;

33: font-size:18px;

34: }

35:

36: h1 {

37: color:#006363;

38: margin:1em;

39: }

40:

41: a {

42: color:#ff7373;

43: font-size:20px;

44: }

45:

46: li {

47: line-height:1.5em;

48: }

49:

50:

51: ” .. a(“Home”, ”/”) .. ” - ” .. a(“New”, “/new”) .. "

" .. title .. "

" .. body .. ""

52: )

53:

54: # Actions

55:

56: render_index := method(params,

57: db open

58: posts := db exec(“SELECT * from posts”)

59: db close

60:

61: posts_html := posts map(post, li( a( post at(“title”), post at(“url”) ) ) ) join

62:

63: with_template(“Io News”, ul(posts_html))

64: )

65:

66: render_new := method(params,

67: with_template(“New”, form(“/create”, field(“title”) .. field(“url”) .. submit() ))

68: )

69:

70: render_create := method(params,

71: db open

72: db exec(“INSERT into posts (title, url)

73: values (’#{params at(\“title\”)}’, ’#{params at(\“url\”)}’)” interpolate)

74: db close

75: with_template(“Hurray!”, “Io rocks!”)

76: )

77:

78: not_found := method(

79: with_template(“Not found”)

80: )

81:

82: # Unfortunately I had to manually extract the parameters

83:

84: extract_parameters := method(string,

85: # foo=bar&x=y => list(list(“foo”, “bar”), list(“x”, “y”))

86: l := string split(”&”) map(param, param split(”=”))

87:

88: params := Map clone

89: l foreach(param, params atPut(param at(0), param at(1)))

90: params

91: )

92:

93: handle_request := method(request,

94: path_and_parameters := request split(”?”)

95: path := path_and_parameters at(0)

96:

97: if(path_and_parameters size > 1,

98: parameters := extract_parameters(path_and_parameters at(1)),

99: parameters := nil

100: )

101:

102: # Does anyone know how to implement cond()?

103: if(path == ”/”,

104: render_index(parameters),

105: if(path == “/new”,

106: render_new(parameters),

107: if(path == “/create”,

108: render_create(parameters),

109: not_found

110: )

111: )

112: )

113: )

114:

115: WebRequest := Object clone do(

116: handleSocket := method(aSocket,

117: aSocket streamReadNextChunk

118: request := aSocket readBuffer betweenSeq(“GET ”, ” HTTP”)

119: aSocket streamWrite(handle_request(request))

120: aSocket close

121: )

122: )

123:

124: WebServer := Server clone do(

125: setPort(8000)

126: handleSocket := method(aSocket,

127: WebRequest clone @handleSocket(aSocket)

128: )

129: )

130:

131: WebServer start

如果你想运行代码，你可能需要先建立一个数据库结构，下面是我的步骤：

1: db := SQLite clone

2: db setPath(“news.sqlite”)

3: db open

4: db exec(“CREATE TABLE posts(id INTEGER PRIMARY KEY ASC,

5: title VARCHAR(255),

6: url VARCHAR(255),

7: published_at DATE)”)

9: db exec(“INSERT INTO posts (title, url, published_at)

10: values

11: (‘Welcome aboard’, ‘http://example.com’, DATETIME(‘NOW’))”)

12:

13: db exec(“INSERT INTO posts (title, url, published_at)

14: values

15: (‘Io documentation’, ‘http://www.iolanguage.com/scm/io/docs/IoGuide.html’, DATETIME(‘NOW’))”)

16:

17: db close

结果如下：

个人而言，我非常喜欢IO语言，我可能会多学习它几天时间。