Erlang Jump Start

Short and to the point introduction into Erlang Programming language and ideas behind it.

Covered:
- Functional Programming Ideas
- Erlang as a Functional Language
- Erlang Data Types
- Erlang Concurrency Model
- OTP Introduction
- Useful Erlang Tools (eunit, rebar, cover, xref)

Presented on ULCamp::Dev (http://ulcamp.ru/dev) on June, 15th 2013.

Transcript

1. Erlang
   Jump Start
   Alexander Zhuravlev, Echo Inc.
   http://aboutecho.com
   @zaa
   
   

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2. Where
   do I Start?
   
   

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3. http://learnyousomeerlang.com
   

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5. http://learnyouhaskell.com
   

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6. http://www.erlang.org/doc/
   http://erldocs.com/
   Reference Documentation
   

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7. Books
   

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8. Erlang
   
   

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9. Erlang is
   Erlang (the language)
   +
   OTP (Open Telecom Platform)
   +
   ERTS (Erlang RunTime System)
   

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10. Erlang (the language)
    Functional
    Strict evaluation
    Dynamic typing
    Concurrency oriented
    

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11. Erlang Selling Points
    Built in concurrency model
    Fault tolerance
    Soft realtime
    Pattern matching
    SMP support out of the box
    Very simple language
    

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12. Erlang History
    1986 First version in Prolog
    1990 Added distribution
    1997 BEAM VM in C
    1998 Open sourced
    2006 SMP support
    

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13. Getting
    Started
    
    

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14. Installation
    https://www.erlang-solutions.com/downloads/
    Erlang installation distributives for all major
    operating systems: Windows, Mac OS X, Linux
    

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15. Erlang Shell
    zmac:~>  erl
    Erlang  R16B  (erts-­‐5.10.1)  [source]  [64-­‐bit]  [smp:2:2]  [async-­‐
    threads:10]  [hipe]  [kernel-­‐poll:false]  [dtrace]
    Eshell  V5.10.1    (abort  with  ^G)
    1>  help().
    **  shell  internal  commands  **
    b()                -­‐-­‐  display  all  variable  bindings
    e(N)              -­‐-­‐  repeat  the  expression  in  query  
    ...
    

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16. First Module
    -­‐module(example).
    -­‐export([sum/2]).
    sum(X,  Y)  -­‐>  X  +  Y.
    zmac:~>  erl
    Erlang  R16B  (erts-­‐5.10.1)  [source]  [64-­‐bit]  [smp:2:2]  [async-­‐
    threads:10]  [hipe]  [kernel-­‐poll:false]  [dtrace]
    Eshell  V5.10.1    (abort  with  ^G)
    1>  c(example).
    {ok,example}
    2>  example:sum(1,  2).
    3
    

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17. First Modification
    -­‐module(example).
    -­‐export([sum/2,  product/2]).
    sum(X,  Y)  -­‐>  X  +  Y.
    product(X,  Y)  -­‐>  X  *  Y.
    3>  c(example).
    {ok,example}
    4>  example:product(1,  2).
    2
    

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18. Data
    Types
    
    

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19. Data Types
    Integer
    123456789
    16#deadbeef
    Not limited in size
    Float 1.20E-10 64 bit
    Atom ok Not garbage collected
    Reference #Ref<0.0.0.59>
    Unique value from
    make_ref/0
    Binary <<139,123>> Sequence of bytes
    Pid <0.45.0> Process ID
    Port #Port Port ID from open_port/2
    Fun #Fun First class function
    

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20. Collections
    List [1,2,3]
    Tuple {1, “two”, ‘three’}
    String “Hello, World”
    Record #example{field = “Value”}
    

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21. List Comprehensions
    zmac:~>  erl
    Erlang  R16B  (erts-­‐5.10.1)  [source]  [64-­‐bit]  [smp:2:2]  [async-­‐
    threads:10]  [hipe]  [kernel-­‐poll:false]  [dtrace]
    Eshell  V5.10.1    (abort  with  ^G)
    1>  [X  +  1  ||  X  <-­‐  [1,  2,  3]].
    [2,3,4]
    2>  [X  +  Y  ||  X  <-­‐  [1,2,3],  Y  <-­‐  [10,  100,  1000]].
    [11,101,1001,12,102,1002,13,103,1003]
    3>  [X  +  Y  ||  X  <-­‐  [1,2,3],  Y  <-­‐  [10,  100,  1000],  X  +  Y  >  1000].
    [1001,1002,1003]
    

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22. Property Lists
    zmac:~>  erl
    Erlang  R16B  (erts-­‐5.10.1)  [source]  [64-­‐bit]  [smp:2:2]  [async-­‐
    threads:10]  [hipe]  [kernel-­‐poll:false]  [dtrace]
    Eshell  V5.10.1    (abort  with  ^G)
    1>  PL  =  [{a,  "value  for  a"},  {b,  "value  for  b"}].
    [{a,"value  for  a"},{b,"value  for  b"}]
    2>  proplists:get_value(a,  PL,  "default  value").
    "value  for  a"
    3>  proplists:get_value(c,  PL,  "default  value").
    "default  value"
    

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23. Functional
    Programming
    ∞
    

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24. In functional programming, programs are
    executed by evaluating expressions, in
    contrast with imperative programming where
    programs are composed of statements which
    change global state when executed.
    Functional Languages Philosophy
    

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25. λ-calculus
    vs
    Turing machine
    

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26. First class functions
    Higher-order functions
    Immutable data
    Referential transparency
    Recursion
    Tail call optimization
    Pattern matching
    Functional Languages Properties
    

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27. Functions as Values
    zmac:~>  erl
    Erlang  R16B  (erts-­‐5.10.1)  [source]  [64-­‐bit]  [smp:2:2]  [async-­‐
    threads:10]  [hipe]  [kernel-­‐poll:false]  [dtrace]
    Eshell  V5.10.1    (abort  with  ^G)
    1>  Sum  =  fun(X,  Y)  -­‐>  X  +  Y  end.
    #Fun
    2>  Sum(2,  3).
    5
    

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28. Functions in Modules
    -­‐module(example2).
    -­‐export([sumList/1]).
    sumList(List)  -­‐>  sumList(List,  0).
    sumList([],  Acc)  -­‐>  Acc;
    sumList([H|T],  Acc)  -­‐>  sumList(T,  H  +  Acc).
    

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29. Higher Order Functions
    -­‐module(example3).
    -­‐export([sumList/1]).
    sumList(List)  -­‐>
       lists:foldl(
           fun(X,  Acc)  -­‐>
               X  +  Acc
           end,
           0,  List).
    

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30. Currying
    zmac:~>  erl
    Erlang  R16B  (erts-­‐5.10.1)  [source]  [64-­‐bit]  [smp:2:2]  [async-­‐
    threads:10]  [hipe]  [kernel-­‐poll:false]  [dtrace]
    Eshell  V5.10.1    (abort  with  ^G)
    1>  Sum  =  fun(X)  -­‐>  fun(Y)  -­‐>  X  +  Y  end  end.
    #Fun
    2>  Sum(1).
    #Fun
    3>  (Sum(1))(2).
    3
    4>  SumOne  =  Sum(1).
    #Fun
    5>  SumOne(5).
    6
    

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31. Concurrency
    Model
    
    

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32. Processes
    spawn_link
    spawn_monitor
    Pid1
    ☰ Pid2
    ☰
    Pid2
    ☰
    Pid1
    ☰
    message queue
    

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33. Message Passing
    zmac:~>  erl
    Erlang  R16B  (erts-­‐5.10.1)  [source]  [64-­‐bit]  [smp:2:2]  [async-­‐
    threads:10]  [hipe]  [kernel-­‐poll:false]  [dtrace]
    Eshell  V5.10.1    (abort  with  ^G)
    1>  Self  =  self().
    <0.32.0>
    2>  Pid  =  spawn(fun()  -­‐>  receive  ping  -­‐>  Self  !  pong  end  end).
    <0.35.0>
    3>  Pid  !  ping.
    ping
    4>  Result  =  receive  Value  -­‐>  Value  after  5000  -­‐>  timeout  end.
    pong
    5>  Result.
    pong
    

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34. Distributed
    Nodes
    
    

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35. Distributed Nodes
    zmac:~>  erl  -­‐sname  foo  -­‐setcookie  testcookie
    Erlang  R16B  (erts-­‐5.10.1)  [source]  [64-­‐bit]  [smp:2:2]  [async-­‐
    threads:10]  [hipe]  [kernel-­‐poll:false]  [dtrace]
    Eshell  V5.10.1    (abort  with  ^G)
    (foo@zmac)1>  net_adm:ping(boo@zmac).
    pong
    zmac:~>  erl  -­‐sname  boo  -­‐setcookie  testcookie
    Erlang  R16B  (erts-­‐5.10.1)  [source]  [64-­‐bit]  [smp:2:2]  [async-­‐
    threads:10]  [hipe]  [kernel-­‐poll:false]  [dtrace]
    Eshell  V5.10.1    (abort  with  ^G)
    (boo@zmac)1>  net_adm:ping(foo@zmac).
    pong
    

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36. OTP
    ⚙
    

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37. Generic Behaviours
    supervisor Supervision trees
    gen_server Server
    gen_fsm Finite State Machine
    gen_event Event Processing
    application Applications
    

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38. gen_server behaviour
    -­‐module(counter_server).
    -­‐behaviour(gen_server).
    -­‐export([incr/0]).
    -­‐export([init/1,  handle_call/3,  handle_cast/2,  handle_info/2,  
    start_link/0]).
    start_link()  -­‐>
           gen_server:start_link({local,  ?MODULE},  ?MODULE,  [],  []).
    incr()  -­‐>
           gen_server:call(?MODULE,  incr).
    init(_Args)  -­‐>
           {ok,  0}.
    handle_call(incr,  _From,  Counter)  -­‐>
           {reply,  Counter,  Counter  +  1}.
    

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39. Tools
    ⚒
    

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40. Tools
    eunit Unit/Integration Testing
    ct Integration Testing
    cover Code coverage
    xref Cross reference checks
    rebar Build tool
    escript Erlang as script
    

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41. EUnit
    -­‐module(example5).
    -­‐export([sumList/1]).
    -­‐include_lib("eunit/include/eunit.hrl").
    sumList(List)  -­‐>  lists:sum(List).
    sumList_test()  -­‐>
                       ?assertEqual(3,  sumList([1,  2])).
    1>  c(example5).
    {ok,example5}
    2>  eunit:test(example5).
       Test  passed.
    ok
    3>  eunit:test(example5,  [verbose]).
    ========================  EUnit  ========================
    example5:  sumList_test  (module  'example5')...ok
    =======================================================
       Test  passed.
    ok
    

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42. Rebar
    {deps,  [
       {lager,  "2.0.0",  
             {git,  "git://github.com/basho/lager.git",
                 {tag,  "e749242087706e480ecb530d99c5615e7e0dc7d6"}}}
       ]}.
    {erl_opts,  [{parse_transform,  lager_transform},  debug_info]}.
    {cover_enabled,  true}.
    {xref_checks,  [undefined_function_calls,undefined_functions]}.
    {post_hooks,  [
       {compile,  "rm  -­‐rf  ./apps/popcorn/ebin/*.mustache;"},
       {compile,  "cp  ./apps/popcorn/priv/templates/*.mustache  ./
    apps/popcorn/ebin"}
    ]}.
    

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43. Questions?
    Alexander Zhuravlev
    zaa@ikato.com
    @zaa
    
    

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