erlang introduction bcberlin3
TRANSCRIPT
Erlang Introduction
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Syntax
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Hello User
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erl
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$ erl1> |
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1> io:format("Hello User~n", []).Hello Userok
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2> 1 + 2008.2009
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3> 1 + 2 + 3.6
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10> 1 + 2 * 3.711> 2 * 3 + 1.712> (1 + 2) * 3.9
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13> 3/0.** exception error: bad argument in an arithmetic expression in operator '/'/2 called as 3 / 0
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4> catch 3/0.{'EXIT',{badarith,[{erlang,'/',[3,0]}, {erl_eval,do_apply,5}, {erl_eval,expr,5}, {shell,exprs,6}, {shell,eval_exprs,6}, {shell,eval_loop,3}]}}
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15> "Erlang intro"."Erlang intro"
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35> "abc" ++ "def"."abcdef"
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27> [72, 101, 108, 108, 111]."Hello"
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27> [$E, $r, $l, $a, $n, $g]."Erlang"
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Atom
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6> atom.atom
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oktruefalsekernelerlang'EXIT''Name'
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6> is_atom(zbar).true
9> 1 == 3.false
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Use Functions
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36> lists:reverse("nilreB olleH")."Hello Berlin"
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1> Mod = lists.lists2> Fn = reverse.reverse3> Mod:Fn("tac")."cat"
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5> Mod:(list_to_atom("reverse"))("ate"). "eta"
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37> apply(lists, reverse, ["nilreB"])."Berlin"
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39> Fn = fun lists:reverse/1.#Fun<lists.reverse.1>40> apply(Fn, ["olleH"])."Hello"
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Variables
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48> N = 1.149> N = 2.** exception error: no match of right hand side value 250> N = 1.1
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Pattern matchingand Variables
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2> {espresso, _, Crema} = Coffee.{espresso, "Harem", orange}
1> Coffee = harem:espresso().{espresso, "Harem", orange}
3> Crema.orange
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Data Structures
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[101, left, right, $a, [0, 1, 2], "abc"]
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5> L = [101, left, right, "abc"]. [101,left,right,"abc"]
6> lists:nth(1,L). 101
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7> lists:nthtail(1, L). [left,right,"abc"]
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29> [66, 101 | "rlin"]."Berlin"
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38> [First, Sec | Rest] = "Rest"."Rest"
39> First.82
40> [First]."R"41> Sec.10142> [Sec]. "e"
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Strings sind Listen
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Tuple
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{1, 2, 3}
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1> P = {adam,24,{july,29}}.{adam,24,{july,29}}
2> element(1,P).adam
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3> element(3,P).{july,29}
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4> P2 = setelement(2,P,25).{adam,25,{july,29}}
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5> tuple_size(P).3
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Binaries
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<<13, 10, 13, 10>>
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<<"GET / HTTP/1.1">>
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web_request(Req) -> Req:ok({"text/html", <<"<html> <head><title> Hello Berlin </title></head> <body> Hello Berlin </body> </html>">>}).
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0000000 d4 c3 b2 a1 02 00 04 00 00 00 00 00 00 00 00 000000010 60 00 00 00 01 00 00 00 07 aa f7 48 b4 32 08 000000020 4e 00 00 00 4e 00 00 00 00 14 6c 62 ef 18 00 190000030 e3 07 c0 bc 08 00 45 00 00 40 30 0d 40 00 40 060000040 3e 4e c0 a8 b2 cb d1 55 87 93 cd b9 00 50 a1 590000050 7f 98 00 00 00 00 b0 02 ff ff ad c0 00 00 02 040000060 05 b4 01 03 03 03 01 01 08 0a 27 c0 a6 25 00 000000070 00 00 04 02 00 00 0000076
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<<Version:4, IHLen:4, TOService:8, TotalLength:16, Id:16, Flags:3, FragOffset:13, Ttl:8, Protocol:8, HeaderChecksum:16, SourceAddr:32, DestAddr:32>> = H.
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43> A = 0.044> B = 8.845> C = 15.1546> Msg = <<A:9, B:12, C:16>>.<<0,0,64,0,15:5>>
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dictarraysetssofs
digraph
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Module file
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-module(forest).-export([tree/1, tree/2]).
-include_lib("kernel/include/flora.hrl").
%% External API
tree(Age) -> {tree, Age}.tree(Age, Kind) -> {tree, Age, Kind}.
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forest.erl
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$ erlc forest.erl
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forest.beam
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Define Functions
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double(X) -> 2 * X.
greet(Name) -> io:fwrite("Hallo ~p~n", [Name]),
ok.
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1, 2, 3, 5, 8, 13, 21, 34, 55, 89
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fib(0) -> 0;fib(1) -> 1;fib(N) when is_integer(N) -> fib(N-1) + fib(N-2).
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For Want Of Loop
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Recursion
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vowels(Text) -> vowels(Text, []).
vowels([H|T], Acc) -> Acc1=case member(H, "aeiuo") of true -> [H | Acc]; false -> Acc end, vowels(T, Acc1);vowels([], Acc) -> reverse(Acc).
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foo(N) when N > 1 -> ok.
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bar(N) when is_list(N), length(N) ->
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baz(I) when I > 0, I < 9 ->
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quux(K) when I =< 0 or I >= 9 ->
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double(N) when is_number(N) -> N * 2;double(N) when is_list(N) -> N ++ N.
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process("/customer" ++ QString) -> customer(QString);
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process("/customer" ++ QString) -> customer(QString);process("/employee" ++ QString) -> employee(QString);process(Any) -> ok.
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Concurrent programming
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Shared state
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Message passing
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spawn(Fun)
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Pid = spawn(Fun)
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Pid ! {lookup, {name, "Carl"}}
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receive {lookup, Query} -> query(Query)end
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receive {lookup, Query} -> query(Query); {update, Update} -> update(Update)end
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receive Any -> Anyend
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link(Pid)
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process_flag(trap_exit, true)
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{'EXIT', From, Reason}
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1> self().<0.89.0>
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Distributed Erlang
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spawn(Node, Fun)
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Node = 'serv@flomac'.
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node()
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nodes()
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net_adm:ping(Node)
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Function Functions
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lists
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mapfoldlfilter
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lists:map(Fun, List)
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L = [1,2,3,4,5],L1 = lists:map(fun(E) -> E * 2 end, L).[2,4,6,8,10]
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lists:foldl(Fun, Acc, List)
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L = [1,2,3,4,5],L1 = lists:foldl(fun(E, Acc) -> Acc + E end, L).
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lists:filter(Fun, List)
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L = [1,2,3,4,5],L1 = lists:filter(fun(E) -> E rem 2 == 0 end, L).[2,4]
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rpc:pmap({Module, Function}, ExtraArgs, List2)
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OTP
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Supervision Tree Behaviours
Applications
Releases
Up- & Downgrades
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{ch3, start_link, []}
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init(_Args) -> {ok, {{one_for_one, 1, 60}, [{ch3, {ch3, start_link, []}, permanent, brutal_kill, worker, [ch3]}] }}.
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Behaviour
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Impl
Base Class
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Callback
Behaviour
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Library
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kernel
rpc
erlang file
inetapplication io
error_logger
code
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stdlib
filename
dictmath
stringsets
dets regexpproplists
arrayrandom
queue timer
shell
gen_server
lists
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Do stuff
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Unit Tests
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succeed() -> ok.
fail() -> throw(failed).
succeeding_test() -> succeed().
failing_test() -> fail().
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succeeding_assert_test_() -> ?_assert(1 > 0).
failing_assert_test_() -> ?_assert(0 > 1).
succeeding_error_test_() -> ?_assertError(foo, erlang:error(foo)).
failing_error_test_() -> ?_assertError(foo, erlang:throw(foo)).
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File IO
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{ok, Binary} = file:read_file(Filename)
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{ok, Terms} = file:consult(Filename)
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Macros
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?MODULE?LINE
-define(OK, "200").?OK
-define(trace(A), ...)?trace
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Hello world
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$ sudo port install mochiweb$ escript /opt/local/share/scripts/ \ new_mochiweb.erl my \ app$ cd myapp ; make$ sh start-dev.sh
$ open localhost:8000
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536 SeitenJuli '07
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Record
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-record(person, {name, age}).
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.hrl
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new(Name, Age) -> #person{name=Name, age=Age}.
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name(P) -> P#person.name.
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rename(P, NewName) -> P#person{name=Name}.
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Where Next?
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400 SeitenMärz '09
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500 SeitenMai '09
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portsedoc
debuggererlang-mode
disteltype specsdialyzer
mochiwebyaws
Lisp Flavoured ErlangReia
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OTP Behaviours
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gen_server
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gen_fsm
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supervisor
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-module(sup).-behaviour(supervisor).
-export([start_link/0]).-export([init/1]).
start_link() -> supervisor:start_link(sup, []).
init(_Args) ->...
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application
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filename:dirname( code:which(?MODULE))
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11> {ok,File} = file:open("PROJECTS", [read]).{ok,<0.92.0>}13> io:get_line(File, [])."Intro Erlang (am Mi., 17.10.08)\n"15> file:close(File).
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