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Hey, Erlang

Pre-alpha Kottans courses

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Erlang data types and primitives

Lecture 3.

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Erlang types of data types

Erlang types of data types

  • Basic data types

Erlang types of data types

  • Basic data types
  • Pseudo-types

Erlang types of data types

  • Basic data types
  • Pseudo-types
  • User-defined types

Erlang types of data types

  • Basic data types
  • Pseudo-types
  • User-defined types
  • Reference

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Basic data types

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Basic data types

Number

Basic data types

Number

  • can be integer or float

Basic data types

Number

  • can be integer or float
  • can be negative or positive

Basic data types

Number

  • can be integer or float
  • can be negative or positive
  • can be written in various forms

Basic data types

Number

  • can be integer or float
  • can be negative or positive
  • can be written in various forms
1> 42. % positive integer
42
2> -42. % negative integer
-42
3> 16#FF. % number with base 16
255
4> 32#LOL. % number with base 32
22293
5> 32#lol. % numbers are case insensitive
22293
6> $Q. % character codes are numbers
81
7> $q. % they are case sentisive
113

Basic data types

Number

  • can be integer or float
  • can be negative or positive
  • can be written in various forms
1> 12.345. % positive float
12.345
2> -12.345. % negative float
-12.345
3> 12.0E0. % float in power of 10 notation ==> 12.0 * 10^0
12.0

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Basic data types

Atom

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Basic data types

Atom

--- # Basic data types ## Atom --- # Basic data types ## Atom
  • takes predefined place in memory like symbol in Ruby

Basic data types

Atom

  • takes predefined place in memory like symbol in Ruby
  • starts with lowercase

Basic data types

Atom

  • takes predefined place in memory like symbol in Ruby
  • starts with lowercase
  • can contain spaces if quoted with single quotes

Basic data types

Atom

  • takes predefined place in memory like symbol in Ruby
  • starts with lowercase
  • can contain spaces if quoted with single quotes
  • can contain any symbol if quoted with single quotes

Basic data types

Atom

  • takes predefined place in memory like symbol in Ruby
  • starts with lowercase
  • can contain spaces if quoted with single quotes
  • can contain any symbol if quoted with single quotes
1> symbol. % just simple symbol
symbol
2> symbol_with_underscores. % symbol with underscores
symbol_with_underscores
3> 'Quoted symbol with spaces'. % quoted symbol with spaces
'Quoted symbol with spaces'

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Basic data types

Tuple

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Basic data types

Tuple

--- # Basic data types ## Tuple --- # Basic data types ## Tuple
  • surrounded by curly brackets {}

Basic data types

Tuple

  • surrounded by curly brackets {}
  • can contain all other data types

Basic data types

Tuple

  • surrounded by curly brackets {}
  • can contain all other data types
  • can contain tuples too

Basic data types

Tuple

  • surrounded by curly brackets {}
  • can contain all other data types
  • can contain tuples too
  • can be used in pattern matching to extract information

Basic data types

Tuple

  • surrounded by curly brackets {}
  • can contain all other data types
  • can contain tuples too
  • can be used in pattern matching to extract information
1> {42, 42, 42}. % tuple with integers
{42, 42, 42}
2> {}. % empty tuple
{}
3> {atom, 42, {another_tuple}}.
{atom, 42, {another_tuple}}
4> {name, Name} = {name, 'Joe'}. % extracting data by pattern matching
{name, 'Joe'}
5> Name.
'Joe'
6> {name, Name2} = {name}. % mismatch will lead to exception
** exception error: no match of right hand side value {name}

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Basic data types

List

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Basic data types

List

--- # Basic data types ## List --- # Basic data types ## List
  • surrounded by square brackets []

Basic data types

List

  • surrounded by square brackets []
  • can contain all other data types

Basic data types

List

  • surrounded by square brackets []
  • can contain all other data types
  • can contain lists too

Basic data types

List

  • surrounded by square brackets []
  • can contain all other data types
  • can contain lists too
  • can be used in pattern matching to extract information

Basic data types

List

  • surrounded by square brackets []
  • can contain all other data types
  • can contain lists too
  • can be used in pattern matching to extract information
  • effective grows to the left, not effective to the right

Basic data types

List

  • surrounded by square brackets []
  • can contain all other data types
  • can contain lists too
  • can be used in pattern matching to extract information
  • effective grows to the left, not effective to the right
1> []. % empty list
[]
2> [atom, 42, {tuple}, [list]]. % list with data
[atom, 42, {tuple}, [list]]
3> [H | T] = [1, 2, 3]. % usign pattern matching to extract head and tail of list
[1, 2, 3]
4> H. % head of list
1
5> T. % tail of list
[2, 3]
6> [5 | T]. % adding element to head of list
[5, 2, 3]
7> [5] ++ T. % merge lists
[5, 2, 3]

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Basic data types

Binary

Basic data types

Binary

Basic data types

Binary

  • can represent plain binary data

Basic data types

Binary

  • can represent plain binary data
  • can represent strings

Basic data types

Binary

  • can represent plain binary data
  • can represent strings
  • contains plain bits

Basic data types

Binary

  • can represent plain binary data
  • can represent strings
  • contains plain bits
  • pattern matching can be used to extract values

Basic data types

Binary

  • can represent plain binary data
  • can represent strings
  • contains plain bits
  • pattern matching can be used to extract values
1> Color = 16#FFFFFF. % bind Color variable
16777215
2> Pixel = <<Color:24>>. % use Color variable as 24-bit binary
<<"ÿÿÿ">> % this was because of heuristic string detection
3> <<R:8, G:8, B:8>> = Pixel.
<<"ÿÿÿ">>
4> R.
255
5> <<F:16, Rest/binary>> = Pixel. % pattern matching with type postfix
<<"ÿÿÿ">>
6> F.
65535
7> Rest.
<<"ÿ">>

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Basic data types

Functions

Basic data types

Functions

Basic data types

Functions

  • can be anonymous or named

Basic data types

Functions

  • can be anonymous or named
  • have arity

Basic data types

Functions

  • can be anonymous or named
  • have arity
  • used in generators and can accept other functions as arguments

Basic data types

Functions

  • can be anonymous or named
  • have arity
  • used in generators and can accept other functions as arguments
1> F1 = fun(X) -> X * 2 end.
#Fun<erl_eval.6.90072148>
2> F2 = fun hello_world:hello/0.
#Fun<hello_world.hello.0>
3> F1(5).
10
4> F2().
Hello world!
ok
5> F3 = fun(X) -> X() end.
#Fun<erl_eval.6.90072148>
6> F3(F2).
Hello world!
ok

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Basic data types

PIDs

Basic data types

PIDs

Basic data types

PIDs

  • PID is process identifier

Basic data types

PIDs

  • PID is process identifier
  • PID consists of node number, first 15 bits of process number, bits 16-18 of process number

Basic data types

PIDs

  • PID is process identifier
  • PID consists of node number, first 15 bits of process number, bits 16-18 of process number
  • can be converted from other data types (but needs special format)

Basic data types

PIDs

  • PID is process identifier
  • PID consists of node number, first 15 bits of process number, bits 16-18 of process number
  • can be converted from other data types (but needs special format)
  • message can be sent to PID
1> PID = self().
<0.43.0>
2> PID ! ok.
ok
3> PID2 = list_to_pid("<0.239.0>").
<0.239.0>

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Pseudo-types

Pseudo-types

  • String. String is enclosed in double quotes "" and actually is a shorthand for list

Pseudo-types

  • String. String is enclosed in double quotes "" and actually is a shorthand for list
  • Record. Record is special guarded format for tuple

Pseudo-types

  • String. String is enclosed in double quotes "" and actually is a shorthand for list
  • Record. Record is special guarded format for tuple
  • Boolean. Boolean is just atoms true and false

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Pseudo-types

String

Pseudo-types

String

Pseudo-types

String

  • detected from list heuristically

Pseudo-types

String

  • detected from list heuristically
  • concatenated if written adjacent (only for 2 adjacent strings)

Pseudo-types

String

  • detected from list heuristically
  • concatenated if written adjacent (only for 2 adjacent strings)
  • operates as list in BEAM

Pseudo-types

String

  • detected from list heuristically
  • concatenated if written adjacent (only for 2 adjacent strings)
  • operates as list in BEAM
1> "hello". % plain string
"hello"
2> [$h, $e, $l, $l, $o]. % plain list
"hello" % was detected heuristically
3> "he" "llo". % concatenation
"hello"
4> "he" ++ "llo" % joining lists
"hello"

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Pseudo-types

Records

Pseudo-types

Records

Pseudo-types

Records

  • Created for data storage

Pseudo-types

Records

  • Created for data storage
  • Fields can be referenced by their atom names

Pseudo-types

Records

  • Created for data storage
  • Fields can be referenced by their atom names
  • Internally represented as a tuple {type, Field1, Field2, ..., FieldN}

Pseudo-types

Records

  • Created for data storage
  • Fields can be referenced by their atom names
  • Internally represented as a tuple {type, Field1, Field2, ..., FieldN}
  • Syntax of definition differs for source files and shell

Pseudo-types

Records

  • Created for data storage
  • Fields can be referenced by their atom names
  • Internally represented as a tuple {type, Field1, Field2, ..., FieldN}
  • Syntax of definition differs for source files and shell
1> rd(person, {name = "", phone = [], address}). % declare record
person
% actually analog of `-record(person, {name = "", phone = [], address}).` in source file
2> #person{phone=[0,8,2,3,4,3,1,2], name="Robert"}.
#person{name = "Robert",
        phone = [0,8,2,3,4,3,1,2],
        address = undefined}
3> #person{name = "Jakob", _ = '_'}. % non-explicit fields definition
#person{name = "Jakob",phone = '_',address = '_'}
4> P = #person{name = "Joe", phone = [0,8,2,3,4,3,1,2]}.
#person{name = "Joe",phone = [0,8,2,3,4,3,1,2],address = undefined}
5> P#person.name. % access record field
"Joe"
6> rf(). % forgot ALL record definitions
[]
7> P. % record is actually stored as tuple
{person,"Joe",[0,8,2,3,4,3,1,2],undefined}

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Pseudo-types

Boolean

Pseudo-types

Boolean

Pseudo-types

Boolean

  • true and false actually are atoms

Pseudo-types

Boolean

  • true and false actually are atoms
  • this is all you need to know about booleans in Erlang

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User-defined types

User-defined types

User-defined types

  • consists from set of predefined types

User-defined types

  • consists from set of predefined types
  • can not be named as already existant builtin types

User-defined types

  • consists from set of predefined types
  • can not be named as already existant builtin types
  • can not be declared in shell

User-defined types

  • consists from set of predefined types
  • can not be named as already existant builtin types
  • can not be declared in shell

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Reference

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Reference is unique across all the connected Universe!

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Type guards

Type guards

Type guards

  • is_atom/1, is_binary/1, is_bitstring/1, is_boolean/1, is_float/1, is_function/1
  • is_integer/1, is_list/1, is_number/1
  • is_pid/1, is_port/1, is_record/2
  • is_record/3, is_reference/1, is_tuple/1

Type guards

  • is_atom/1, is_binary/1, is_bitstring/1, is_boolean/1, is_float/1, is_function/1
  • is_integer/1, is_list/1, is_number/1
  • is_pid/1, is_port/1, is_record/2
  • is_record/3, is_reference/1, is_tuple/1
  • There is no typeof function in Erlang. Because let it crash.

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End of Lecture 3

Subject of next lecture: Advanced Erlang code structures. Bye, shell!

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Bye, folks!

Joe with notebook