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Welcome to the
Scalable Language
Ahmed Soliman
Founder and Chairman
noZom NGO

Tuesday, May 24, 2011

AhmedSoliman.com

Asoliman@nozom.org

@AhmedSoliman

Martin Odersky
Switzerland


✦ 52 years old

✦ Pizza Programming
language

✦ Generic Java

✦ Scala 2001

@odersky

What is Scala?


What is Scala?

✦ Pronounced ‘skah-lak’
✦ Scalable Language
✦ Tastefully typed language
✦ Blend of object-oriented and functional
programming


What is Scala?

✦ Uses the glorious JVM
✦ Can be used as scripting language
✦ Compiled!
✦ Everything is an expression!


Expression vs. Statement


Grows on you

✦ Looks like modern dynamically typed
languages (Python, Ruby, etc.)
✦ Unlike Python, maps in scala is not a language
syntax! {‘key’: ‘value’}


Growing new types

✦ BigInt looks like a built-in type, because you
can use integer literals and operators such as
(*, -, and +) with values of that type


What makes Scala scalable?
✦ Scala is object oriented in pure form!
✦ Every value is an object and every
operation is a method call
✦ Scala is full-blown functional programming
language


Functional?

✦ Lisp late 50s
✦ Scheme, SML, Erlang, Haskell, OCaml, and
F#
✦ For long time, popular in academia, but not in
industry


What’s functional?

✦ Functions return a value, given a set of
parameters a function has one possible result.


Two Main Ideas: I

Functions are ﬁrst-class citizens


Citizens?
✦ A function is a value of the same status as, say,
an integer or a string.
✦ You can pass functions as arguments to other
functions
✦ Return functions as a results from functions
✦ Store them in variables


Functions, citizens?
✦ You can deﬁne functions without giving them
a name, sprinkling your code with function
literals as easy as integer literals, like 25

✦ A good example is the pain in writing code for
event handling in java


This is Java


Two Main Ideas: II
✦ Operations of a program should map input
values to output values rather than change
data in place
✦ Consider the difference between Strings in
Java and Ruby!
✦ Immutable data structures are the
cornerstone of functional programming


Referential
Transparency


State is the evil!
Pun intended


Multi-core problems
✦ The future!
✦ Threading is damn hard to get right
✦ Memory overhead
✦ Dead locks?
✦ Shared state? Monitor? Mutex?
Semaphore?
✦ Demand for highly concurrent application is
increasing

Why Scala?


Why Scala?
✦ The Java Virtual Machine
✦ Concise (programs are shorter)


Why Scala??
✦ A rich static type system that gets out of your
way when you don’t need it, is awesome when
you do. (Type Inference). Veriﬁable!

✦ Flexible syntax

✦ Immutable and mutable variables


Why Scala??

✦ Functional programming features: mapping,
ﬁltering, folding, currying, so much more.
✦ FAST! (most of the times as fast as Java)
✦ Can call any Java code
✦ Can be called by any Java code


Mapping


Reducing

21


Pattern Matching


Currying


Concurrency

✦ Actor model! (kinda like erlang)
✦ Threads
✦ Any other JVM concurrency framework
(Netty, Apache Mina, etc.)


Concurrency :: Actor
✦ Actor Mode: a different way to implement
concurrency
✦ Each object is an actor
✦ Each actor has a mailbox
✦ Actors (asynchronously) send messages and
receive them in their mailbox
✦ No Shared State
✦ Why?

Actors :: Performance
✦ Apache (C/Threads) vs. Yaws (Erlang/Actor)


Actors :: Simpler

✦ Code is design around single-threaded mind
✦ No Mutable State
✦ No (Dead) lock


Language Tour


What for?


✦ Scripting
✦ Concurrent Applications
✦ Web Development (Lift)
✦ Backend Components


Who uses Scala?


Summary
✦ Fast
✦ Reuses the Java Ecosystem
✦ Functional
✦ Expressive
✦ Statically typed
✦ Concurrent
✦ Has tons of features, complex? Worth it!

www.nozom.org

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