1. Introduc)on to Erlang
Abd El‐Fa3ah Hussein Mahran

2. Agenda
 History of Erlang
 Erlang Features
 Erlang/OTP and design patterns
 Tools applications
 Applications written in Erlang
 Erlang IDEs
 Erlang syntax
 How to get Erlang
 Demo
 Conclusion
 Q&A

3. History of Erlang
 Erlang is a programming
language
 Ericsson wanted
programming language for
developing
telecommunication switching
systems.
 The language must be a very
high level symbolic language
in order to achieve
productivity gains
 The language must contain
primitives for concurrency
and error recovery

4. History of Erlang
1998:
No language well suited Open Source
for telecom systems Erlang
1984: development
Ericsson
Computer
Science Lab 1991:
formed First fast
implementation
1987:
1984-86: Early Erlang
Experiments Prototype 1996:
programming projects Open Telecom Platform
POTS with (research on verification...)‫‏‬
several languages 1995:
Several
new projects
1993:
Distributed
Erlang

5. Erlang is Concurrent functional
programming language
It was designed by Ericsson to support distributed, fault-tolerant,
soft-real-time, and non-stop applications

6. Erlang Features
 Concurrency
 Fault tolerance
 Soft Real-Time
 Distribution
 Hot Code Loading
 External Interfaces
 Platform Independent

7. Erlang/OTP and design patterns
 Gen_Server Behaviour
 Gen_Fsm Behaviour
 Gen_Event Behaviour
 Supervisor Behaviour
 Releases
 Target systems

8. Tools applications
 Dialyzer
 Eunit
 Edoc
 Common_test
 Test_server
 Jinterface
 Erl_interface
Depending on
 wx
C++ WXwidgets
 Ssh
 Ssl
 xmerl

9. Applications written in Erlang

10. Applications written in Erlang
 Ericsson Company  Netkit Solutions (Network Equipment Monitoring
and Operations Support Systems)
 Bluetail/Alteon/Nortel (distributed, fault tolerant
email system, SSL accelerator)  Process-one (Jabber Messaging)
 Cellpoint (Location-based Mobile Services)  Schlund + Partner (Messaging and Interactive
Voice Response services)
 Corelatus (SS7 monitoring).
 Quviq (Software Test Tool)
 dqdp.net (in Latvian) (Web Services).
 RabbitMQ (AMQP Enterprise Messaging)
 Facebook (Facebook chat backend)
 T-Mobile (previously one2one) (advanced call
 Finnish Meteorological Institute (Data acquisition control services)
and real-time monitoring)
 Telia (a telecomms operator)
 IDT corp. (Real-time least-cost routing expert
systems)  Vail Systems (Interactive Voice Response
systems)
 Kreditor (Electronic payment systems)
 Wavenet (SS7 and IVR applications)
 Mobilearts (GSM and UMTS services)

11. Erlang IDEs
 Eclipse (ErlIDE plugin)
 NetBeans (ErlyBird)
 Emacs
 VIM
 Any other editor (Gedit, Notepad++)

12. Erlang syntax
 Data types
 If statement
 Case statement
 Functions
 Modules
 Hello World program
 How Erlang works

13. Data types
 Number
 Integer 12, 43
 Float 34.3
 Atoms create, remove
 Binaries <<“hello”>>
Erlang don’t have
 Reference boolean as data
 Fun type, instead Erlang
 Port Identifier has true and false
 Pid <0,36,0>
 Tuple {1, 2, 3}
 List [1, 2, 3, 4]
 String “hello”
 Record -record(person, {name, age, phone}).

14. If statement
if
GuardSeq1 ->
Body1;
...;
GuardSeqN ->
BodyN
end.

15. Case Statement
case Expr of
Pattern1 [when GuardSeq1]->
Body1;
...;
PatternN [when GuardSeqN] ->
BodyN
end.

16. Functions
Clause 1 Name(Pattern11,...,Pattern1N) [when GuardSeq1] ->
Body1;
...;
Clause 2 Name(PatternK1,...,PatternKN) [when GuardSeqK] ->
…..,
BodyK.
Parameters
Conditions
Function name
Body

17. Modules
-module(moduleName).
-export([func/0, func/1]).
func() ->
foo(5),
….
func(A) ->
foo(A),
….
foo(N) ->
…,
…,
...

18. Hello world Program
Save the file as
“hello_world.erl”, After
-module(hello_world). compilation output will
be “hello_world.beam”
-export([print/0]).
$ erl
Eshell V 5.7.1 (abort with ^G)
print() -> 1> c(hello_world).
{ok, hello_world}
io:format(“Hello World…!~n”). 2> hello_world:print().
Hello World…!
3>

19. How Erlang works
 Pattern matching technique
 Var = 3.
 [Var1, Var2] = [3, 4].
 {Var3, _Var4, Var5} = {4, 5, a}.
 [H | T] = [iti, erlang, course, book].
1 = 1.
{ok, Var} = {ok, “Connected to DB”}. √
1 = 2.
{ok, var} = {ok, “Connected to DB”}. X

20. Recursion and Tail Recursion
fact(0) -> fact(N) ->
1; fact_help(N, 1).
fact(N) when N>0 ->
N * fact(N -1). fact_help(0, Acc) ->
Acc;
fact_help(N, Acc) when N>0 ->
NewAcc = N * Acc,
fact_help(N-1, NewAcc).

21. Quick Sort
quicksort([]) -> % If the list [] is empty, return an empty list (nothing to sort)
[];
quicksort([Pivot|Rest]) ->
quicksort([Front || Front <- Rest, Front < Pivot])
++ [Pivot] ++
quicksort([Back || Back <- Rest, Back >= Pivot]).

22. How to get Erlang
 Erlang.org
 Download
 Documentation
 Trapexit.org
 Erlang Factory
 Erlang-Consulting

23. Demo
 Hot Code swapping
 Concurrency
 Fault tolerance
 Distributed application

24. Hot Code swapping
-module(changing_code).
-export([start/0, loop/0]).
% Forces the use of
start() ->
loop/0 from
spawn(changing_code, loop, []).
the latest version of
loop() -> changing_code
receive
switch ->
changing_code:loop();
hello ->
io:format(“CAT Hackers ----1~n”),
loop();
Msg ->
io:format(“~p~n”, [Msg]),
loop(),
end.

25. Concurrency
portscan(Ip, From, To) when From < To ->
io:format("Ports open for: ~p:~n", [Ip]),
pforeach(fun(Port) -> scan(Ip,Port) end,lists:seq(From, To)).
scan(Ip, Port) ->
case gen_tcp:connect(Ip,Port,[{active, false}, binary]) of
{ok,P} ->
gen_tcp:close(P),
io:format("~p is open~n", [Port]);
_ ->
ok
end.
pforeach(F, [H|T]) ->
spawn(fun() -> F(H) end),
pforeach(F, T);
pforeach(_ , []) ->
ok.

26. Fault tolerance
init([]) ->
AChild=
{main_module,{main_module, start_link, []}, permanent,
2000, worker, [main_module]},
{ok,{{one_for_one, 1, 60}, [AChild]}}.

27. Distributed application
Timeout to wait until
restart application on
Nodes
other node
[{kernel,
[{distributed,
[{dist_app, 5000, [‘node1@ricsson.com’, {‘node2@ricsson.com’, ‘node3@ricsson.com’}]}]},
{sync_nodes_mandatory, [‘node2@ricsson.com’, ‘node3@ricsson.com’]},
{sync_nodes_timeout, 5000} ] } ].
Specifies how many
milliseconds to wait for
the other nodes to
start

28. Conclusion
 Erlang is concurrent functional programming
language.
 Its main goal is error recovery, fault tolerant,
distributed applications, and non-stop applications.
 It released to Open source since 1998.
 Companies that are using Erlang.
 How Erlang works.
 How to get and use Erlang.

29. References
 Erlang.org
 Trapexit.org
 Programming Erlang, Joe Armstong
 Wikipedia.com

30. Q&A

31. Thanks