Erlang Jump Start - Speaker Deck

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

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Where do I Start? 

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http://learnyousomeerlang.com

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No content

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http://learnyouhaskell.com

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

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Books

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Erlang

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

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

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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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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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Getting Started

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

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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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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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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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Data Types

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

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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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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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Functional Programming ∞

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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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λ-calculus vs Turing machine

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

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

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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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Concurrency Model

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

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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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Distributed Nodes

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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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OTP ⚙

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

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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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Tools ⚒

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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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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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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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Questions? Alexander Zhuravlev [email protected] @zaa 