My notes on learning Elixir from https://elixir-lang.org/getting-started/

You need access to Elixir REPL for trying out the example. Install at https://elixir-lang.org/install.html

Getting into the Elixir REPL

You can use the iex command to enter into the REPL after installing it.

Getting help

Use the h

iex> h Kernel.trunc

If the function has multiple signatures, specify the number of signatures to select the function.

iex> h Kernel.trunc/1

Booleans

true and false

You can compare like

true == false

Checking data type

is_boolean, is_integer, is_float, is_number etc.

Atoms (Symbols)

They are constants.

Example

:apple, :orange etc

Atoms are equal if the names are equal

iex> :apple == :orange`
true

true and false are also atoms. You can skip : for them.

> :true == true
true

Strings

Encoded using double quotes.

Supports string interpolation.

iex> string = "hello"
"hello"
iex> "#{string} world"
"hello world"

You can print using

iex> IO.puts("hello")
hello
:ok

Strings are represented as bytes. ö takes 2 bytes to be represnted in UTF-8.

You can concatenate strings using <>

iex(47)> x = "hello"
"hello"
iex(48)> y = "world"
"world"
iex(49)> x <> " " <> y
"hello world"

iex> is_binary("hellö")
true
iex> byte_size("hellö")
6
iex> String.length("hellö")
5
iex> String.upcase("hello")
"HELLO"

Anonymous functions

iex> add = fn a, b -> a + b end
#Function<43.40011524/2 in :erl_eval.expr/5>
iex> add(1, 3)
** (CompileError) iex:5: undefined function add/2

iex> add.(1, 3)
4
iex> is_function(add)
true

The . is required to distinguish between normal functions.

You can access the variables that are in scope when the function is defined.

iex> x = 7
7
iex> print_x = fn -> IO.puts(x) end
#Function<45.40011524/0 in :erl_eval.expr/5>
iex> print_x.()
7
:ok

Variabled declared inside the function does not affect the surrounding environment

#Function<45.40011524/0 in :erl_eval.expr/5>
iex> y = 2                  
2
iex> set_y = fn -> y = 3 end
warning: variable "y" is unused (there is a variable with the same name in the context, use the pin operator (^) to match on it or prefix this variable with underscore if it is not meant to be used)
  iex:14

#Function<45.40011524/0 in :erl_eval.expr/5>
iex> set_y.()
3
iex> y
2

Lists

Lists are implemented as Linked Lists.

iex> list = [1, 2, "three", :four, true, false]  
[1, 2, "three", :four, true, false]

You can concatenate or subtract lists. Returns a new list. The Elixr data structures are immutable.

iex(17)> list = [1, 2, "three", :four, true, false]  
[1, 2, "three", :four, true, false]
iex(18)> [1, 2] ++ [3, 4]
[1, 2, 3, 4]
iex(19)> [1, 2, 3, 4, 5, true, false] -- [4, 5, false]
[1, 2, 3, true]

Head is the first element and tail is the remaining elements.

iex(23)> hd(x)
1
iex(24)> tl(x)
[2, 3, 4, 5]

You can use length to get the length of the list. Since list is a linked list the length operation takes linear time. In general, "length" is used to refer for operations that take linear time and size is used for operations that don't constant time.

Tuples

Tuples are stored continously in memory.

iex> x = {1, "2", :hello, true, [1, 2]}
{1, "2", :hello, true, [1, 2]}

So unlike lists you can access them using index.

iex> elem(x, 2)                        
:hello

You can also change the element of a tuple and returns a new tuple. The new tuple share the elements with the old tuple except the one that has been replaced.

iex(38)> x
{1, "2", :hello, true, [1, 2]}
iex(39)> put_elem(x, 3, :world)
{1, "2", :hello, :world, [1, 2]}
iex(40)> x
{1, "2", :hello, true, [1, 2]}

You can use the tuple_size function to get the size of the tuple.

iex(42)> x            
{1, "2", :hello, true, [1, 2]}
iex(43)> tuple_size(x)
5

Boolean operators

Similiar to Python, there is and and or for evaluating boolean values.

iex(55)> true and false        
false
iex(56)> false and true
false
iex(57)> true or false
true
iex(58)> true or raise("Error")
true

Unlike Python the left hand operator has to be a boolean.

iex(62)> true and 1      
1
iex(63)> 1 or true
** (BadBooleanError) expected a boolean on left-side of "or", got: 1

iex(63)> 1 and true
** (BadBooleanError) expected a boolean on left-side of "and", got: 1

iex(63)> true or 1
true
iex(64)> true and 3
3

But there are the traditional ||, && and ! operators which can be evaulated using any data typles. 0 is not considered to be false.

iex(86)> nil && 1 
nil
iex(87)> nil && 2
nil
iex(88)> true and 2          
2
iex(89)> true and 3
3
iex(90)> 0 || 5
0
iex(91)> false || 5
5
iex(92)> false || 0
0
iex(93)> false && true
false
iex(94)> 0 && true    
true
iex(95)> 0 && nil 
nil
iex(96)> nil && 1
nil