Scala is a multi-paradigm programming language that supports both object-oriented programming and functional programming. Some key features of Scala include: 1. Support for OOP concepts like abstraction, inheritance, polymorphism, and types. 2. Support for functional programming concepts like lambda calculus, higher-order functions, immutability, pattern matching, and tail call optimization. 3. Ability to create internal and external domain-specific languages (DSLs) to provide customized syntax and functionality for a specific problem domain.

1. scala['skeilə] 东白

2. scala?OOPFPDSL

3. OOP?数据的抽象化(data abstraction)继承(inheritance)多态(ploymorphism)模块化(module)复用(reuse)类型(type)

4. FP?lambda calculuslambda x . plus x x(lambda x . plus x x) y rule: alpha – 变量替换 beta – 值应用{lisp[ML/erlang/haskell]}functionisvalue[hightorderfunction]; nosideeffect; lazy evaluation; pattern match; currying/partial funcitons; tail recursion optimization; etc…

5. DSL?definition: Domain-Specific Languages/领域特定语言internal DSL便于用库来提供语言特性 easy debug etc…external DSL easy design and write[withparser] newsyntax etc…

6. not simple?

7. base1.原生类型是对象的实例123.toByte"1".toInttrue.toString2.函数也是值val compare = (x: Int, y: Int) => x > ycompare(1, 2) // result: Boolean = false3.变量varVal/lazy val4.字面量/literalsvali = 1234356; //Intval l = 123454L; // Longval f = 0.123; // Floatval c = 'a' or '\u0041'; //Chaarval s = "string" or """ String "ssssss'""" //Stringval symbol = 'name [scala.Symbol("programming scala") //symbol5.Predef.scala一切操作都是函数一切操作都返回值}=>

9. trait

10. companion objects

11. parameterized typesinvariant/不变: C[T], C is invariant on T如果Tsub或Tsup是T的子类或超类，C[Tsub]或C[Tsup]都不是C[T]类covariant/协变: C[+T], C is covariant on T如果Tsub是T的子类，则C[Tsub]也是C[T]的子类Contravatiant/逆变: C[‐T], C is contravariant on T如果Tsup是T的超类，则C[Tsup]也是C[T]的子类

12. implicit and type bounds

13. function

14. functional data structures

15. pattern match & case class

16. concurrent1.thread2.java.util.concurrent3.event/NIO4.Actor ==><==

17. DSL

18. herding xml in scala

19. ETC…

20. THANKS