Functional Leap of
Faith
Tomer Gabel, Wix
JDay Lviv 2014

Through the Looking Glass
20 years ago…
• C/C++ rule the
market [1]
• First release of Java
[1] TIOBE Index (historical data)

… since then?*
• C and Java are neck-and-neck
• Virtual machines are everywhere
• Garbage collection is everywhere
• OOP is everywhere
* Not exhaustive

Virtual Machines
1967 BCPL
1978 UCSD p-System
1994 JVM
2014 Everywhere!

Garbage Collection
1960 Formalized[1]
1970s Research
1994 JVM
2014 Everywhere!
[1] Recursive Functions of Symbolic Expressions and Their Computation by Machine, Part I

Object-Oriented Programming
1967 Simula 67
1980 Smalltalk 80
1983 C++
2014 Everywhere!

Advances take
decades to become
mainstream

Market Growth[1]
3000
2500
2000
1500
1000
500
0
1975 1980 1985 1990 1995 2000 2005 2010 2015* 2020*
Units (Millions)
[1] eTForecasts Worldwide PC Market Research Report

3000
2500
2000
1500
1000
500
0
1975 1980 1985 1990 1995 2000 2005 2010 2015* 2020*
Units (Millions)
Market Growth
• Structured Programming
• Module Systems
• Dynamic Memory Allocation

3000
2500
2000
1500
1000
500
0
1975 1980 1985 1990 1995 2000 2005 2010 2015* 2020*
Units (Millions)
Market Growth
• Garbage Collection
• OOP
• VMs and JIT

3000
2500
2000
1500
1000
500
0
1975 1980 1985 1990 1995 2000 2005 2010 2015* 2020*
Units (Millions)
Market Growth
You are here!

What’s holding us
back?

The Market has Shifted
• SaaS is the norm
• Shorter time to
market
• Latency requirements
are stricter
• Availability is
business-critical

The Free Lunch is Over[1]
[1] The Free Lunch is Over, Herb Stutter (Dr. Dobb's Journal, 2005)
• CPUs aren’t getting
(much) faster
• Rather, they’re getting
parallel
• Concurrency is the
new kid on the block

Datasets are Getting Bigger
• Terabyte-scale data is
common
• Computation demand
– NoSQL
– Big Data
• Specialized hardware
(SAN) is a hindrance

We need new
abstractions.

Three desirable
attributes:

Today’s systems
are highly available & reliable.
Tomorrow’s abstraction must…
encourage correct code.

Complexity is the Mind Killer
• Complex system  bigger codebase
• More code  more bugs
• We want less code
• We want correct code

Control flow  Data flow
We need to invert our thinking.

How  What
We need to invert our thinking.

Control flow describes the
how
List<Person> adults(List<Person> in) {
ArrayList<Person> out = new ArrayList<>();
for (Person p : in)
if (p.getAge() >= 18)
out.add(p);
return out;
}

Data flow describes the what
List<Person> adults(List<Person> in) {
return in.stream()
.filter(p -> p.age >= 18)
.collect(Collectors.toList());
}

“What” is Better
• Focuses on the
problem
• Reduces accidental
complexity
• Decouples intent from
execution

Today’s systems
are highly concurrent.
Tomorrow’s abstraction must…
encourage immutability.

The Case for Immutability
• Inherently thread-safe
• Referentially
transparent
• Easier to reason
about!

Today’s systems
are horizontally scalable.
Tomorrow’s abstraction must…
simplify workload distribution.

Distribution 101
1. Take a core
computation
2. Split it out
3. Run on many nodes
4. Profit

Why is this hard?
• Behavior-as-data
• Side effects
• High-performance
frameworks
 Lambdas
 Immutability
 Akka, Hadoop,
Storm…

The future is
functional.
1. Data flow-oriented
2. Immutable
3. Easy to distribute

tomer@tomergabel.com
@tomerg
http://il.linkedin.com/in/tomergabel
THANK YOU FOR YOUR TIME!