Introduction to Scala

Introduction to Scala

• 1.
  A programming languagefor the JVM (and .net)
• 2.
  Functional / OOhybrid
• 3.
  Statically typed
• 4.
  Compile to classfiles
• 5.
  Iterpretive Console
• 6.
  Flexible syntax Whatis it?
• 7.
  'Scalable Language' Onthe JVM
• 8.
  Integrates with existinglibraries
• 9.
  Integrates readily withother systems (in code XML & JSON support)
• 10.
  Flexible syntax –can be like Java or can move to DSLs and higher abstractions. The name
• 11.
  Removes Java roadblockswithout changing platform or throwing away existing properties Tasks that are difficult or tedious in Java can be simplified with minimal investment in time and tools Rapid development without losing type safety.
• 12.
  Java + newlanguage features: Closures, actors, infix operators, case classes, pattern matching, list and map operations, native XML, implicits, defaults, nested elements, no primitives, currying, sequence comprehension, compound types, structural types, function literals … etc Why should we care?
• 13.
  Code example -Hello World Points of interest: Object keyword
• 14.
  Def keyword
• 15.
  Assignment of codeblock to function
• 16.
  scala.Console
• 17.
  Application trait Seeassociated source files at http://tr.im/jA6A HelloWorld.scala & HelloWorldWithTrait.scala
• 18.
  Using the basicbuilding blocks, we can compose code that looks and feels similar to today's Java. Though not source compatible. Can't compile Java. Package, import, class, object, trait, var, val, def
• 19.
  Code example: CatRelaxed naming constraints, constructor arg visibility, constructor overload, function definition, implied static typing, val vs var The basic building blocks Cat.scala
• 20.
  Can be veryterse
• 21.
  Return type impliestype of function
• 22.
  Naming is greatlyrelaxed.
• 23.
  Code sample: RationalSymbols as function names -> infix operators, optional 'return' keyword, if statements are ternary, DSLs Functions Rational.scala
• 24.
  XML is anative datatype
• 25.
  Rich XML operationsmake parsing and creating XML simple.
• 26.
  Code sample: NativeXMLEclipse plugin slightly broken – parentheses not required, XML direct in code, nested values, iterated lists, xpath-like functions Native XML NativeXML.scala
• 27.
  Implicit functions mapone type to another
• 28.
  Ascribes new functionalityto old friends e.g. Make the JDBC library user-friendly Code sample: UpperCaseAwareString RichString already exists
• 29.
  Implicit def declaration
• 30.
  Multiple impicit defs,but method calls must be unambiguous at compilation Extending other classes – Monkey Patching UpperCaseCharAwareString.scala
• 31.
  Compile time checkedduck typing
• 32.
  Can define typesbased on functions signatures
• 33.
  Code sample: DuckType keyword, multiple method definitions, includes param and return types, can be inlined Structural types – Duck Typing Duck.scala
• 34.
  More than interfaces
• 35.
  Less than classes
• 36.
  Act as markers
• 37.
  Can have methods
• 38.
  Can have constructors
• 39.
  Code sample: BraviaExtend abstract or trait, mixins Traits Bravia.scala
• 40.
  Define combinations oftypes in contracts
• 41.
  Code sample: ChessCompile time type checking for multiple types Compound types chess.Chess.scala
• 42.
  Case objects areakin to enums
• 43.
  Case classes areparameterisable
• 44.
  Pattern Matching isakin to switch statement, but more powerful
• 45.
  Code sample: MonthsNo new keyword, no params for object - params for class, match & case, _ wildcard, exposed params when matching on classes, also used for exception handling Case objects/classes and pattern matching Months.scala
• 46.
  Functions are objects.Everything is!
• 47.
  Can access parentscope (closure)
• 48.
  Can be definedinline ('function literal')
• 49.
  Code sample: BookReaderFunction as a parameter, function knows and can modify instance values, functions defined inline. Functions are objects too BookReader.scala
• 50.
  Any number ofenumerations and filters mixed together to form a new list.
• 51.
  Enumerations add values,filters remove them.
• 52.
  Lightweight notation
• 53.
  Code sample: CondimentsNote generics, note also list creation. Sequence Comprehensions Condiments.scala
• 54.
  Functions with manyparams can be decomposed into a chain of functions.
• 55.
  This is supportedand used to construct language extensions.
• 56.
  Code sample: AutoResourceManagementPartial function takes var args of Closable type, chained function takes a function that takes no params and returns nothing (Unit), makes AOP mainly redundant, note foreach and exception syntax. Currying AutoResourceManagement.scala
• 57.
  www.scala-lang.org Binaries, source,tutorials and doco [email_address] - mailing list
• 58.
  http://groups.google.com/group/scala-melb -Scala Melbourne User Group
• 59.
  http://tr.im/jzQK –Scala for Java devs. Getting started
• 60.
  Testing http://www.artima.com/scalatest/
• 61.
  http://code.google.com/p/specs/
• 62.
  http://code.google.com/p/scalacheck/ Building http://code.google.com/p/simple-build-tool/IDE Support Eclipse, NetBeans, IntelliJ Tools