Erlang was invented in 1986 by Joe Armstrong for building fault-tolerant telecom systems at Ericsson. It achieved 99.9% uptime in these systems. Some key reasons to use Erlang include its ability to easily write concurrent and distributed programs, build highly available systems, and take advantage of multicore processors. Popular applications built with Erlang include WhatsApp, RabbitMQ, Riak, and Ejabberd. The document then provides examples of basic Erlang concepts like arithmetic, variables, atoms, tuples, lists, strings, and pattern matching. It also shows how to compile and run a simple "Hello World" program.

1. Erlang Intro
Balaji G

2. History
● Joe Armstrong Invented Erlang (he is no more with us)
● Created in 1986 for ericsson telecom systems ,
● Open-sourced in 1998 by ericsson
● Achieved uptime 99.9% in telecom systems

3. 5 Reasons to Learn Erlang By Author Joe
Here are five reasons why you should learn Erlang:
• You want to write programs that run faster when you run them on a multicore
computer.
• You want to write fault-tolerant applications that can be modified without taking them
out of service.
• You’ve heard about “functional programming” and you’re wondering whether the
techniques really work.
• You want to use a language that has been battle tested in real large-scale industrial
products that has great libraries and an active user community.
• You don’t want to wear your fingers out by typing lots of lines of code.

4. WHY ERLANG?
❖ There are so many programming Languages c, c++, java, python, ruby,
haskell, java, scala etc
❖ Scalability
❖ High Performance
❖ Fault Tolerance
❖ Concurrency

5. Things Created in Erlang
➔ Whatsapp
➔ RabbitMQ (Message Broker)
➔ Mnesia
➔ RIAK Database (No SQL, Key- value data store)
➔ Ejabberd

6. Installation
sudo apt-get install erlang

7. Starting Erlang Shell
bala@bala:~$ erl
Erlang/OTP 21 [erts-10.2.4] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1]
Eshell V10.2.4 (abort with ^G)
1>
q(). % to quit erl shell
Cntl + G to abort shell
i interrupt current shel
j list current shell details

8. Lets See Some Arithmetic
Operations

9. 1> 5/3.
1.66667
2> 4/2.
2.00000
3> 5 div 3.
1
4> 5 rem 3.
2
5> 4 div 2.
2
Basic Operations
6> Pi = 3.14159.
3.14159
7>R = 5.
5
8> Pi * R * R.
78.5397

10. Variables
1. Should be Start with UPPER CASE Letter
2. Once assigned Value that can’t be changed .
3. (e.x) X = 10 , you can’t change the value of X into something else
4. Erlang Strictly follows Mathematics L.H.S = R.H.S
5. X = 6.
6. X = 4+ 2.
7. X = 10.
** exception error: no match of right hand side value 10

11. Atoms
Atoms Used to represent non numerical constants in Erlang , similar to
enumerated constants in C language
# define OP_READ 1
1> hello.
hello
2> monday.
monday
3>

12. Tuples
● Group fixed number of items in to a single entity , it is similar to struct in c
● In C Struct Point {
Int x,
Int y;
} P;
● P = {10, 45} % it denotes the Point X, Y
● In Erlang , the is no type declarations .
1>Person ={person, {name, bala}, {height, 5.4}, {eyecolor, brown}}.
{person,{name,bala},{height,5.4},{eyecolor,brown}}

13. Extracting Values from Tuples
Point = {point, 10, 45}.
{point, X, Y} = Point.
3> X.
10
4> Y.
45

14. Pattern Matching in detail
Eshell V10.2.4 (abort with ^G)
1> Person ={person, {name, bala}, {height, 5.4}, {eyecolor, brown}}.
{person,{name,bala},{height,5.4},{eyecolor,brown}}
2> {_,{_, Who}, _, _} = Person.
{person,{name,bala},{height,5.4},{eyecolor,brown}}
3> Who.
bala
hyphen(_) is called “Anonymous variable” in Erlang . It’s like a placeholder we are
not interested in it or don’t want the values of those.

15. Lists
1>L = [1,2,3,4,5].
● First element of the list is called “Head”
● Rest of the elements in list called “Tail” (This always should be list)
● Reading Head in O(1) , it’s always efficient in Erlang
● In Erlang we always pick head , and do operation
● [Head, Tail] = L.
● Head.
1
● Tail.
[2,3,4,5]

16. List Inbuilt Operations
4> L = [1,3,4,5].
[1,3,4,5]
5> lists:sum(L).
13
6> lists:max(L).
5
7> lists:min(L).
1

17. List Comprehensions
1> [2*N || N <- [1,2,3,4]].
[2,4,6,8]
2> [X || X <- [1,2,3,4,5,6,7,8,9,10], X rem 2 =:= 0].
[2,4,6,8,10]
3> [X+Y || X <- [1,2], Y <- [3,4]].
[4,5,5,6]

18. Strings
● String are enclosed in double quotes in Erlang (“) , Note in other
programming string can be single or double quotes but in erlang only double
quotes.
● > Name = “Balaji”.
“Balaji”
● Literally there are no strings in erlang it’s just a numbers in erlang
● To know which integer represents which character use dollar syntax
● 1> $a.
97

19. Does That Mean Erlang is Poor in String
Processing?
● Don’t lose hope , Erlang factory is an organisation has
created an “Artifical Intelligence “ for Robots in Erlang .
●

20. Hello World In Erlang
-module(hello).
-export([hello/0]).
hello() -> io:fwrite("Hello World!").

21. Compiling and Running Erlang Code
bala@bala:~/erlcodes/codes/othercodes$ erl
Erlang/OTP 21 [erts-10.2.4] [source] [64-bit] [smp:4:4]
[ds:4:4:10] [async-threads:1]
Eshell V10.2.4 (abort with ^G)
1> c(hello).
{ok,hello}
2> hello:hello().
Hello World!ok

22. Factorial Program in Erlang
-module(fac).
-export([fac/1]).
fac(0) -> 1;
fac(N) -> N*fac(N-1).
1> c(fac).
{ok, fac}
2> fac:fac(5).
120

23. Books to Learn Erlang
● Programming Erlang By “Joe Armstrong” (Creator of
Erlang)
● Learn You Some Erlang By “Fred Hebret”
● Erlang and OTP in Action by “Martin Logan”

24. Questions ?

25. Thanks !!!