A programming language for the JVM (and .net) Functional / OO hybrid Statically typed Compile to class files Iterpretive Console Flexible syntax What is it?

A programming language for the JVM (and .net)

Functional / OO hybrid

Statically typed

Compile to class files

Iterpretive Console

Flexible syntax

'Scalable Language' On the JVM Integrates with existing libraries Integrates readily with other systems (in code XML & JSON support) Flexible syntax – can be like Java or can move to DSLs and higher abstractions. The name

'Scalable Language'

On the JVM

Integrates with existing libraries

Integrates readily with other systems (in code XML & JSON support)

Flexible syntax – can be like Java or can move to DSLs and higher abstractions.

Removes Java roadblocks without 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. Java + new language 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?

Removes Java roadblocks without 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.

Java + new language 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

Code example - Hello World Points of interest: Object keyword Def keyword Assignment of code block to function scala.Console Application trait See associated source files at http://tr.im/jA6A HelloWorld.scala & HelloWorldWithTrait.scala

Code example - Hello World

Points of interest:

Object keyword

Def keyword

Assignment of code block to function

scala.Console

Application trait

Using the basic building 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 Code example: Cat Relaxed naming constraints, constructor arg visibility, constructor overload, function definition, implied static typing, val vs var The basic building blocks Cat.scala

Using the basic building 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

Code example: Cat

Relaxed naming constraints, constructor arg visibility, constructor overload, function definition, implied static typing, val vs var

Can be very terse Return type implies type of function Naming is greatly relaxed. Code sample: Rational Symbols as function names -> infix operators, optional 'return' keyword, if statements are ternary, DSLs Functions Rational.scala

Can be very terse

Return type implies type of function

Naming is greatly relaxed.

Code sample: Rational

Symbols as function names -> infix operators, optional 'return' keyword, if statements are ternary, DSLs

XML is a native datatype Rich XML operations make parsing and creating XML simple. Code sample: NativeXML Eclipse plugin slightly broken – parentheses not required, XML direct in code, nested values, iterated lists, xpath-like functions Native XML NativeXML.scala

XML is a native datatype

Rich XML operations make parsing and creating XML simple.

Code sample: NativeXML

Eclipse plugin slightly broken – parentheses not required, XML direct in code, nested values, iterated lists, xpath-like functions

Implicit functions map one type to another Ascribes new functionality to old friends e.g. Make the JDBC library user-friendly Code sample: UpperCaseAwareString RichString already exists Implicit def declaration Multiple impicit defs, but method calls must be unambiguous at compilation Extending other classes – Monkey Patching UpperCaseCharAwareString.scala

Implicit functions map one type to another

Ascribes new functionality to old friends

e.g. Make the JDBC library user-friendly

Code sample: UpperCaseAwareString

RichString already exists

Implicit def declaration

Multiple impicit defs, but method calls must be unambiguous at compilation

Compile time checked duck typing Can define types based on functions signatures Code sample: Duck Type keyword, multiple method definitions, includes param and return types, can be inlined Structural types – Duck Typing Duck.scala

Compile time checked duck typing

Can define types based on functions signatures

Code sample: Duck

Type keyword, multiple method definitions, includes param and return types, can be inlined

More than interfaces Less than classes Act as markers Can have methods Can have constructors Code sample: Bravia Extend abstract or trait, mixins Traits Bravia.scala

More than interfaces

Less than classes

Act as markers

Can have methods

Can have constructors

Code sample: Bravia

Extend abstract or trait, mixins

Define combinations of types in contracts Code sample: Chess Compile time type checking for multiple types Compound types chess.Chess.scala

Define combinations of types in contracts

Code sample: Chess

Compile time type checking for multiple types

Case objects are akin to enums Case classes are parameterisable Pattern Matching is akin to switch statement, but more powerful Code sample: Months No 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

Case objects are akin to enums

Case classes are parameterisable

Pattern Matching is akin to switch statement, but more powerful

Code sample: Months

No new keyword, no params for object - params for class, match & case, _ wildcard, exposed params when matching on classes, also used for exception handling

Functions are objects. Everything is! Can access parent scope (closure) Can be defined inline ('function literal') Code sample: BookReader Function as a parameter, function knows and can modify instance values, functions defined inline. Functions are objects too BookReader.scala

Functions are objects. Everything is!

Can access parent scope (closure)

Can be defined inline ('function literal')

Code sample: BookReader

Function as a parameter, function knows and can modify instance values, functions defined inline.

Any number of enumerations and filters mixed together to form a new list. Enumerations add values, filters remove them. Lightweight notation Code sample: Condiments Note generics, note also list creation. Sequence Comprehensions Condiments.scala

Any number of enumerations and filters mixed together to form a new list.

Enumerations add values, filters remove them.

Lightweight notation

Code sample: Condiments

Note generics, note also list creation.

Functions with many params can be decomposed into a chain of functions. This is supported and used to construct language extensions. Code sample: AutoResourceManagement Partial 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

Functions with many params can be decomposed into a chain of functions.

This is supported and used to construct language extensions.

Code sample: AutoResourceManagement

Partial 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.

www.scala-lang.org Binaries, source, tutorials and doco [email_address] - mailing list http://groups.google.com/group/scala-melb - Scala Melbourne User Group http://tr.im/jzQK – Scala for Java devs. Getting started

www.scala-lang.org

Binaries, source, tutorials and doco

[email_address] - mailing list

http://groups.google.com/group/scala-melb - Scala Melbourne User Group

http://tr.im/jzQK – Scala for Java devs.

Testing http://www.artima.com/scalatest/ http://code.google.com/p/specs/ http://code.google.com/p/scalacheck/ Building http://code.google.com/p/simple-build-tool/ IDE Support Eclipse, NetBeans, IntelliJ Tools

Testing

http://www.artima.com/scalatest/

http://code.google.com/p/specs/

http://code.google.com/p/scalacheck/

Building

http://code.google.com/p/simple-build-tool/

IDE Support

Eclipse, NetBeans, IntelliJ