Erlang Cheatsheet

Sample program

-module(helloworld).
-export([start/0]).
start() ->
		io:fwrite("Hello World!").

• module : It is used to add a namespace like in other programming language.
• export : Any function which is defined in the program can be used by using export function. /0 means that start function accepts 0 parameters.
• start() : start() is a function
• io : io is an module which has io all the required Input and Output functions.
• fwrite : to output data to the console.
• % : Used to provide comments

Variables

Variables syntax is as follows

variable-name = value

Data types

Data type	Usage	Description
Numeric	start() -> io:fwrite("~w",[10+10]).	Erlang supports both integer and float values.
Atom	start() -> io:fwrite(true)	Atoms should start with lower case leters and can contain lowercase and uppercase characters, numbers, _ and @. You can also put atom in single quotes
Boolean	start() -> io:fwrite(10 =< 8)	Output will be either true or false based on the values given
Bit String	str = <<10,20>>	Strings are enclosed in << >> and are used to store untyped memory
Lists	[1,2,3]	Lists is a compound data type with Variable number of elements.
Tuples	t = {apple, 100, {orange,50}}	Tuple is a compound data type with fixed number of elements.
Map	map = #{name=>onecompiler,message=>Learning}	Map is a compound data type with a variable number of key-value pairs

Operators

Operator type	Description
Arithmetic Operator	+ , - , * , / , rem, div
Relational Operator	< , > , <= , >=, /= , ==
Logical Operator	and, or, not, xor
Bitwise Operator	band, bor, bnot, bxor

Conditional Statements

1. If-Else

if
condition ->
   true-statement;
true ->
   false-statement
end.

2. Case

case value of
   value1 -> statement1;
   value2 -> statement2;
   valuen -> statementn
end.

Note:

As Erlang is a functional programming language, there are no direct constructs for while, for and other loops. Recursion is the technique followed to implement loops in Erlang.

Function

Defining a function

FunctionName(Pattern1… PatternN) ->
%code

Calling a function

FunctionName(Pattern1… PatternN)