Introduction to Scala @ TWJUG 2010/07

Introduction to Scala @ Taiwan Java User Group 2010/07

Transcript

1. Introduction Scala BrianHsu @ TWJUG
2. 關於我
3. http://bone.twbbs.org.tw/blog/ 墳墓 (BrianHsu)
4. 其實我不懂 Scala
5. Scala 非常難
8. 我只會簡單的部份 但我用得很高興！
9. 特別是拿來當 Script Language
10. 工欲善其事 必先利其器
11. 所有的武林高手 都有趁手的兵刃
12. 程式員的兵器 程式語言
13. 我的個性
14. 粗心、懶
15. 所以 我的兵器在哪？
16. 動態語言
17. 3P 好好玩 Python/Perl/PHP
18. 後起之秀 Ruby
19. 因為粗心
20. 討厭執行期爆炸 def boom puts "Hello World" end puts " 一個小小的 typo" booom
21. 對不起，我是懦夫 我不敢用這些語言
22. 靜態語言
23. 真男人就是要冠 C C 語言
24. D 語言 Haskell
25. 我們最愛的 Java Programming Langauge
26. 我們最恨的 Java Programming Langauge
27. 因為懶
28. public static void main (String [] args) { System.out.println(“Hello World”) }
29. public static void main (String [] args) { System.out.println(“Hello World”) } 浪費生命！
30. println ("Hello World")
32. What is Scala?
33. 樓 梯
34. A Postfunctional Programming Language on Java Virtual Machine
35. Compile to JVM .class Byte Code
36. 理論上 Full Java Interoperability
37. What is Scala?
38. A Scalable Language
39. 會隨 User 變形的程式語言
40. A Scalable Language
41. A Scalable Language
42. Why Scala?
44. 三個願望一次滿足
45. REPL Scripting Compiling
46. REPL
47. Scripting
48. Compiling
49. 三個願望一次滿足
50. Procedure Object Oriented Functional
51. Procedure Programming
52. Object Oriented Programming
53. Functional Programming
54. 三個願望一次滿足
55. Concise Static Typing Duck Typing
56. Concise (Ruby)
57. Concise (Scala)
58. Static Typing (Ruby)
59. Static Typing (Scala)
60. 真、 Duck Typing (Ruby)
61. 偽‧ Duck Typing (Scala)
62. 結論
63. 有 Scala 、無懦夫
64. Scala vs Java
65. Scala compared to Java Scala adds Scala removes + a pure object system - static members + operator overloading - primitive types + closures - break, continue + mixin composition with traits - special treatment of interfaces + existential types - wildcards + abstract types - raw types + pattern matching - enums Modeled in libraries: assert, enums, properties, events, actors, using, queries, …
66. Scala cheat sheet (1): Definitions Scala method definitions: def fun(x: Int): Int = { result } def fun = result Scala variable definitions: var x: Int = expression val x: String = expression Java method definition: int fun(int x) { return result } (no parameterless methods) Java variable definitions: int x = expression final String x = expression
67. Scala cheat sheet (2): Expressions Scala method calls: obj.meth(arg) obj meth arg Scala choice expressions: if (cond) expr1 else expr2 expr match { case pat 1 => expr 1 .... case pat n => expr n } Java method call: obj.meth(arg) (no operator overloading) Java choice expressions, stmts: cond ? expr1 : expr2 if (cond) return expr1; else return expr2; switch (expr) { case pat 1 : return expr 1 ; ... case pat n : return expr n ; } // statement only
68. Scala cheat sheet (3): Objects and Classes Scala Class and Object class Sample(x: Int, val p: Int) { def instMeth(y: Int) = x + y } object Sample { def staticMeth(x: Int, y: Int) = x * y } Java Class with statics class Sample { private final int x; public final int p; Sample(int x, int p) { this.x = x; this.p = p; } int instMeth(int y) { return x + y; } static int staticMeth(int x, int y) { return x * y; } }
69. Scala cheat sheet (4): Traits Scala Trait trait T { def abstractMth(x: String): Int def concreteMth(x: String) = x + field var field = “!” } Scala mixin composition: class C extends Super with T Java Interface interface T { int abstractMth(String x) } (no concrete methods) (no fields) Java extension + implementation: class C extends Super implements T
70. Scala 的特異功能
71. 這次沒唬你 萬物皆物件
72. 你可以這樣 1.toString
73. 我們都知道 toString 是 Method
74. 1+1 + 也是 Method ！
75. 1+2 = 1 .+ (2)
76. 向 static 說再見 預設的 Singleton
77. List.range(1, 5) = List(1,2,3,4,5)
78. List 是 class range 是 class method
79. 錯
80. List 是一個 Singleton 物件！
81. range(1,2) 是一個 instance method
82. 只有一個 唯一的 List 物件
84. 懶人的好幫手之一 Tuple
85. 簡單資料結構
86. 座標 鍵值
88. 懶人的好幫手之二 case calss
91. 加強版的 swtich Pattern Matching
95. 加強版（幾乎沒在用）的 FOR expression
97. 建忘的救星 (2.8.0 才有喔！ ) Default / Named Arguments
99. Function Programming Function Literal
100. Function Programming Closure
101. Function Programming High-Order Function
103. Lazy
105. 可以有實作的 Interface Trait
107. 等等，這是孔明的陷阱！
108. Scala 的限制與臭蟲 • 限制 • Cannot acess static protected Java field. – 對不起， Google Maps API 用到了。 • 臭蟲 • Static Java Inner class 造成 classfile borken / missing dependcy – Google Maps API 踩到地雷了 – Fixed in latest SVN trunk • 解決方式 • 用 Java 寫個 Wrapper 唄 Missing dependency
109. Thanks!