A Tour Of Scala

1. A tour of Scala Francois Armand http://fanf42.blogspot.com June 2009

2. Exploring Scala facets

Genesis

3. Scala is...

Mainstream

4. A scripting language

5. Object Oriented

6. Functional

7. Scalable

8. Background - Martin Odersky history

Pizza 1996

Abetter(morefunctional ) Java

Generics , pattern matching, higher order function

9. On the JVM

Sun interested

Generic Java (GJ) 1998/1999

Generics come in Java 5 (2005) with addition (wildcards...)

10. GJ compiler became the default Javac for Java 1.3

Funnel 2000

Again, on the JVM - Bootstrapping is too expensive

11. Pure academic experiment- too academic

Genesis

12. Scala genesis

Scala since 2002

Martin O. join EPFL cole PolytechniquedeLausane

13. Major rewrite in 2006

14. Current version : 2.7.5 2.8 before end of 2009 (hopefully)

Initial goals

A better Java

15. Object Oriented / Functional Programing real merge

Genesis

16. A mainstream language

General purpose

17. On the JVM

18. Statically typed

19. General purpose

Web framework

20. Business layer

21. Side libraries

Test

22. DSL

Graphical User Interface

Scala is mainstream

23. Scala runs on the JVM

Compile to bytecode

24. Fully compatible with Java

Scala code can call Java methods, select Java field, extends Java classes, implements Java interfaces

25. Without any glue code / specific syntax

26. And the same (almost) holds for the other way

=> all existing Java frameworks are available

27. Performances: on part with Java

Scala is mainstream

28. Statically typed

One of the rare statically typed language on the JVM

29. Type annotation AFTER names

30. With generics and type boundaries

31. With type inference

Scala is mainstream

32. Tooling

Plugins for the 3 main Java IDEs

Netbean and Idea: quite good

33. Eclipse

Better and better

34. One people full time on it

JavaRebel (live class reloading)

Scala plugin

35. Free licences

Scala is mainstream

36. Scripting language

What do you want in a scripting language ?

Quick write / test loop

37. Terse / expressive

38. Duck typing

39. Add methods to existing class

40. Easyly usable, high level data types / control structures

41. Write and test - quickly Scala is a scripting language

Read / Eval / Print Loop (REPL)

Console interpreter

42. Code completion with Scala 2.8

Demo: basic Scala constructs

Value / variable

43. Function definition

44. condition

45. Java without noise

Type inference

46. Optional syntax

return

47. .

48. ;

49. { } for one-line method

50. ( ) when 0 or one argument

51. Apply method

Multi-line strings

No need to escape special chars

Scala is a scripting language Scala is a scripting language

52. Expressive

Factories

Defined for all collections in standard library

Tuples

53. For comprehension

Scala is a scripting language

54. Add methods to existing classes

Implicit conversions

Implicitly call wrappers factories to convert between types

55. Checked at compile time

Ex: ScalaCheck

Implicitly call a wrapper to add should method on object Map


56. Duck typing

If it looks like a duck and quacks like a duck, then it probably is a duck

57. Structural types

Checked at compile time


58. Real scripts, from command line

File helloWorld.scala

59. Executed in a console: ~$ ./helloWorld.scala


60. Scala is Object Oriented

Full OO

61. With Classes and Objects

62. Traits

63. Full OO

No primitive types

Everything is an object

64. Even functions are objects !

No operators

Operator are simple methods

No static

Scala is a object oriented

65. Classes and Objects

class

Usual Java-style classes

66. A default constructor

In class declaration

67. Other constructor MUST derive from that one

object

Scala way for static

68. Singleton object


69. Compared to Java Scala is a object oriented

70. Traits - 1

Interfaces with implementation

71. Add aspects


72. Traits - 2

Stackable


73. Scala is functional

Values for everything

74. Higher order functions

75. Immutability & consistency

76. Pattern matching

77. Functional data structures

78. Currying

79. Lazy constructs

80. And a lot of other things !

81. Values for everyone

Each block is valued

Easy to add logic incrementally

82. Block in function parameters

Scala is functional

83. Higher order function & Closures

Function = first class objects

84. Closure = parameters and properties

Scala is functional

85. Immutability and no Null by default

Val & Value objects

Immutability is easy to achieve

Option type

Null should be avoided

Immutable collections

Available in standard library

Scala is functional

86. Add new control structures

Look natives

Valued blocks

87. + Higher order functions & closures

88. + optional syntax

89. = easy extension of the language by libraries

Ex : no break keyword in Scala: add it yourself !

Scala is functional

90. Functional Data Structures

The almighty List

Methods available for all Collections

Scala is a functional

91. Pattern matching - 1

Switch under vitamins

92. Deconstruct object graph Why ?

Work on semi-structured datas : XML, Rexeps, etc

93. Two many methods needed to have them in a top-level object

94. When methods (or top-level object) not under your control


95. Pattern matching - 2

Case classes

Define your own patterns

96. Automatically add equals/hashcode and Factories for you

97. sealed => compiler checks that all choices are tested


98. Currying

Function with a list of arguments

99. == function with multiple argument lists

100. Define new specialized functions easily

Division of labour


101. Lazy constructs - 1

Lazy = evaluated only when needed


102. Lazy constructs - 2

Create infinite Collections


103. A lots of other things

Self types

104. Abstract type

105. Existential types

106. Type variance

107. Monads

108. Combinatory parsers

109. And a lot more

110. So, Why Scala ?

Scalable language

Scala is deep, not broad

111. Scale in large

Object / class hierarchies, traits compositions

Scale in small

Functional aspects: composable small methods

112. => Unix pipes

Easy to add

New Data types

113. New Control Structures

114. Look native

Great for DSL

115. DSL: Actors Scalable language

116. DSL: XML Scala is a functional

117. Successful (?)

Get more and more attention

6 talks at JavaOne 2009 + ScalaLiftOff one full day of Scala

118. 4 books (and 2 other by the end of 2009)

119. Active mailing list / irc channel

120. Several external commiters on the compiler

Who used it ?

Open Source projects

Lift -http://liftweb.net : web framework,full stack

121. Apache Camel / NetBeans / ScalaSpec / ScalaCheck...

Commercial

Twitter / Sony / Mimesis Republic / EDF trading / SAP

Last words

122. Scala 2.8 preview end of 2009

Redesigned collection library

123. Named and default parameters

124. Package object

125. Scala Swing library

126. Revamped REPL

127. Type specialization

128. Continuation (as a plugin compiler)

Last words

129. Questions ?

http://scala-lang.org

130. http://www.artima.com

Technology

A Tour Of Scala