Why scala - executive overview

Why Scala Executive Overview Razvan Cojocaru – May'10

One Slider
Brevity: Scala programs typically 30-50% less code than Java
Productivity and quality increase
Shorter time-to-market
Technology neutral
Compiles to bytecode and runs on the Java Virtual Machine
J2EE, servlets, all Java libraries etc
Soft landing for Java developers
Language resembles Java, JavaScript and C#
Compatibility from / to Java: could replace classes one at a time
Concepts familiar to C++ developers as well
Advanced DSL capabilities
Reduce integration costs
Rapid prototyping

One Slider (part 2)
Stable, open
Acceptance and adoption ramping up
Excellent new libraries
Language allows creation of a new breed of libraries, reducing code in certain cases by a factor of 10 (GUI (swing, SWT), web/AJAX)
Most useful algorithms built-into libraries
Modern
Combines functional and Object-Oriented
Both compiled and interpreted
Replaces scripting languages and in-house DSL

Background
Programming languages evolve on many levels
Hardware coupling
Tied to hardware / compiled
Running on a Virtual Machine
Abstractions:
Structured, Functional, Object-oriented
Type checking, safety
Compiled, Interpreted
Generic / specific: many languages start with a specific target
Hilarious history of programming languages: http://james-iry.blogspot.com/2009/05/brief-incomplete-and-mostly-wrong.html

Meet Scala: “ items sort (_>_) ”
Scala incorporates and unifies the best features from many previous languages
Runs on the JVM
Functional and Object Oriented
Compiled and Interpreted
Designed with the goal of providing a highly simplified and scalable syntax
All the time-consuming and superfluous “features” of Java were dropped and replaced by a smart compiler that requires less instructions to achieve the same thing
Powerful accompanying libraries, while new ones are created continuously.
Interoperability with all Java libraries and frameworks (J2EE, servlets, JMS etc)

Developer Efficiency
Scala programs are typically 30-50% smaller than Java, so by adopting scala,
Developers can write more functionality, with less code, in less time.
Cooperation (reviews and maintenance) is cheaper
Better quality due to less bugs in production.
Focus on one language/environment, not 10
Most shops use a set of languages and frameworks, shell scripts etc
Scala can displace all those
The biggest gain
Lets developers focus more on the problem, domain and functionality rather than the code-to-write

Typical class definition
class Point {
int x;
int y;
public Point (int ax, int ay) {
this.x = ax;
this.y = ay;
}
public int getX () { return x; }
public int getY () { return y; }
public int setX (int x) { this.x=x }
public int setY (int y) { this.y=y }
}
class Point (var x:int, var y:int)
Scala Java

Typical list operations
employees.sort (
new Comparator{
public int compare(Object emp1, Object emp2){
int emp1Age = ( (Employee) emp1).getAge();
int emp2Age = ( (Employee) emp2).getAge();
if( emp1Age > emp2Age )
return 1;
else if( emp1Age < emp2Age )
return -1;
else
return 0;
}
employees.sort (_.age > _.age)
Java Scala How much time is wasted: writing it? Reviewing? Fixing? Maintaining? How many opportunities for bugs that can be introduced? Does the scala alternative look hard to comprehend or easier?

Learning curve
Base language and libraries
Easy transition from Java, formal training not necessary, lots of materials available
Enough to understand scala and use it efficiently
Advanced features
Training recommended. Steeper learning curve
Many concepts learned in school but forgotten by Java developers
More important for library designers, not every-day programming
Libraries / frameworks
Can re-use all familiar Java libraries
Adopt new scala libraries as needed
Pool of experienced scala developers and trainers growing

Development Environment
Plugins for most IDEs:
Eclipse, NetBeans, IntelliJ Idea, Vi, Emacs :)
Full debugging, syntax highlighting, content assist etc
Plus:
command line and interactive interpreters
Deployment model:
scala-library.jar – yet another jar file... that's it!
Major tools/frameworks
ScalaUnit – upgrade of Junit
Sbt – upgrade of maven
Lift – web framework
Very active online community, forums

Open, stable, adopted
Since 2003
Controlled by EPFL (A Swiss University)
Twitter “Much of Twitter's infrastructure has been ported to Scala, and most new infrastructural projects are being built in the language.” The fact that one of today's leading web enterprises placed a big bet on Scala is more of an endorsement than slow adoption in obscure projects inside any Fortune 100 companies…visibility and proportional “costs of failure” are incomparable.

Babel, meet Scala
All companies use a myriad of languages and frameworks. For instance:
Java, JavaScript, JSP, SQL (server), SQL (client)
Ruby/Rails, PHP
Bash, PowerScript, sed, awk
Don't be fooled: any configuration is a language (Domain Specific Language)
XML this and XML that
Ant, struts, spring, maven
Scala single-handedly displaces all of the above
Platform independent scripting (Java based)
XML built-in but not really needed inside new frameworks
DSL support built-in
Even JavaScript is hidden in web libraries

Adoption path
It may sound risky to adopt a new language, but unifying all in-house development, in time, and focusing on a single language/environment does make sense
Until the next divergence – things evolve
Incremental adoption, across projects and teams
Building knowledge as you go
Can see it as yet-another-library and use in specialized components/tools
Don't want to re-write existing Java code, reuse as is
Compatibility from / to Java: replace classes one at a time, as needed
Need guidelines
Avoid abuse
Give developers time to grow into it

So, why Scala?
There are costs of change, for sure
Learning curve (inefficiency)
Training
Risk
As argued here, once “on Scala”, costs will go down
Can mitigate the risk and costs by ramping up across teams and projects and feedback into other teams and projects
One thing is not usually shown in budgets: cost of opportunity :
Not writing less code
Not introducing less bugs
Not spending less time on reviews, maintenance, refactoring, rewriting…
Not using advanced frameworks and new technologies (actors, DSL)

Links
Real world stories
http:// www.artima.com/scalazine/articles/twitter_on_scala.html
Good brief Scala intro:
http://www.codecommit.com/blog/scala/roundup-scala-for-java-refugees
http://www.scala-lang.org/downloads/distrib/files/website/doc/ProgrammingInScala.pdf
The scala wiki:
http:// scala.sygneca.com /
Download new verions:
http://www.scala-lang.org /
More goodies:
http://www.devoxx.com/download/attachments/1705916/D8_U_08_06_01.pdf
http://www.slideshare.net/michael.galpin/introduction-to-scala-for-java-developers-presentation
http://www.slideshare.net/jboner/pragmatic-real-world-scala-45-min-presentation
Other tools:
ScalaUnit, LiftWeb.

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Why scala - executive overview

by Razvan Cojocaru on Apr 28, 2010

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