Short introduction to the programming language Erlang hold at the GeekGirlMeetup in Berlin 2012

1. Erlang
is not a city in Germany!

2. About me
Monika Moser
@momo13
Software Architect

3. Erlang
is a general-purpose language and
a runtime environment.

4. Language
Functional.
Strict evaluation.
Single assignment.
Dynamic typing.

5. Erlang
has built in support for concurrency,
distribution and fault tolerance.

6. Ericsson Language
since 1986

7. Developed
to build near-real-time fault tolerant
distributed non-stop applications.

8. Used by
CouchDB: NoSQL DB that uses JSON to store data
Facebook: For the chat backend
Wooga: Backend for Facebook games
Klarna: Electronic payment systems

9. Functional
-module(hello).
-export([world/0]).
world() ->
io:format("Hello, world!~n", []).

10. Let it run!
$ erl
Erlang R15B01 (erts-5.9.1) [source] [64-bit] [smp:2:2] [async-threads:0] [hipe]
[kernel-poll:false]
Eshell V5.9.1 (abort with ^G)
1> c(hello).
{ok,hello}
2> hello:world().
Hello, world!
ok

11. Expressions
> % A comment
> 1 + 3.
4
> “This is a string”.
“This is a string”

12. Expressions
> [1, 2, 3].
[1,2,3].
> [72, 101, 108, 108, 111, 33].
“Hello!”

13. Expressions
> Variable = “GeekGirls”.
“GeekGirls”
> Variable = "are boring".
** exception error: no match of right
hand side value "are boring"

14. Pattern Matching
> Tuple = { “Erlang”, “Joe A.”}.
{ “Erlang”, “Joe A.”}.
> { Language, Inventor } = Tuple.
{ “Erlang”, “Joe A.”}.
> Language.
“Erlang”

15. Recursion
fac(0) ->
1;
fac(N) when N > 0, is_integer(N) ->
N*fac(N-1).

16. Higher order functions
> lists:foreach(fun(Word) ->
! ! ! ! io:format("~p~n", [Word])
! ! ! end,
! ! ! ["Geek", "Girl", "Meetup"]
! ! ).
“Geek”
“Girl”
“Meetup”

17. Fun with Lists
List comprehension:
> [ X*X || X <- [2, 3, 4], X rem 2 == 0].
[4,16]

18. Concurrency
Lightweight processes
Message passing primitives

19. Sending Messages
PID ! { message, “Content”}.

20. Receiving Messages
loop() ->
receive
{ message, Content } ->
io:format(“Content: ~p”, [Content]);
loop();
Any ->
io:format(“Received unexpected: ~p”, [Any])
end.

21. Spawning a process
PID = spawn(fun loop/0).
PID ! {message, “GeekGirlMeetup”}.
is_process_alive(PID).
true.
PID ! stop.
is_process_alive(PID).
false.

22. Monitor processes
Processes can be monitored.
EXIT signals with a reason will be
received.
process_flag(trap_exit, true).
{‘EXIT’, From, Reason}.

23. Useful for
Distributed, reliable, concurrent systems