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![A Totally “Unbiased” Comparison In Erlang: List = [1,2,3,4,5]. Doubled = lists:map( fun(I) -> I * 2 end, List). In Java: List<Integer> list = new LinkedList<Integer>() {{ add(1); add(2); add(3); add(4); add(5); }}; List<Integer> doubled = new ArrayList<Integer>(); for(Integer integer : list) { doubled.add(integer.intValue() * 2); } © ThoughtWorks 2008](https://image.slidesharecdn.com/dbyrneerlangmad-1227798457249608-9/85/The-Erlang-Programming-Language-3-320.jpg)
![Pattern Matching 1> MyList = [ “ A ” ]. % declaring a list 2> [Var] = MyList. % implicit declaration 3> io:format(Var). % prints “ A ” 1> MyList = [ “ A ” , “ B ” ]. % declaring a list 2> [_, Var] = MyList. % _ is ignored 3> io:format(Var). % prints B © ThoughtWorks 2008](https://image.slidesharecdn.com/dbyrneerlangmad-1227798457249608-9/85/The-Erlang-Programming-Language-5-320.jpg)
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The Erlang Programming Language
The document introduces the Erlang programming language. Erlang is a functional programming language with built-in support for concurrency and reliability. It uses processes, message passing, and immutable state to enable scalable and fault-tolerant distributed systems. Some key features of Erlang discussed include pattern matching, functions as first-class citizens, and concurrency primitives like spawn, send, and receive.
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The Erlang Programming Language
- 1. The Erlang ProgrammingLanguage Dennis Byrne - ThoughtWorks [email_address] http://notdennisbyrne.blogspot.com/ © ThoughtWorks 2008
- 2. Introduction Not a“shiny new object (or function)” Open sourced by Ericsson Functional Programming Concurrency Reliability ThoughtWorks ! Erlang © ThoughtWorks 2008 Erlang is a functional programming language, with native constructs for concurrency and reliability.
- 3. A Totally “Unbiased”Comparison In Erlang: List = [1,2,3,4,5]. Doubled = lists:map( fun(I) -> I * 2 end, List). In Java: List<Integer> list = new LinkedList<Integer>() {{ add(1); add(2); add(3); add(4); add(5); }}; List<Integer> doubled = new ArrayList<Integer>(); for(Integer integer : list) { doubled.add(integer.intValue() * 2); } © ThoughtWorks 2008
- 4. Single Assignment &Unification I = 4. % assignment I = 4. % unification I = I. % unification 4 = I. % unification I = 5. % throws error :( © ThoughtWorks 2008
- 5. Pattern Matching 1> MyList = [ “ A ” ]. % declaring a list 2> [Var] = MyList. % implicit declaration 3> io:format(Var). % prints “ A ” 1> MyList = [ “ A ” , “ B ” ]. % declaring a list 2> [_, Var] = MyList. % _ is ignored 3> io:format(Var). % prints B © ThoughtWorks 2008
- 6. Functions as FirstClass Citizens 1> Msg = "I am scoped". 2> F = fun()-> io:format(Msg) end. 3> F(). % prints “ I am scoped ” © ThoughtWorks 2008
- 7. Tail Recursion Tailrecursion is to ‘recursion’ as optimistic locking is to ‘locking’. loop() -> io:format( “ in constant space ” ), loop() . Automatic byte code manipulation Last call optimization © ThoughtWorks 2008
- 8. Pop Quiz: EvaluationStrategies f( a(), b() ) Order of evaluation Lazy or strict? Left, right, both, neither? © ThoughtWorks 2008
- 9. State Erlang avoidscomplex solutions in favor of simple ways to avoid the problem State is immutable w/ single assignment State is private, passed by value Changing Perspectives Contention vs. Scale Side Effects vs. Scale © ThoughtWorks 2008
- 10. Erlang Process AnErlang process combines the best of An operating system process An operating system thread A “green thread” Controlled in user space by the ERTS Costs less than 300 bytes Private heap Private stack All processes are created equal Incremental garbage collection © ThoughtWorks 2008
- 11. The Actor ModelAsynchronous Message passing Messages passed by value, not reference One to one relationship An Actor A mailbox A Process A Process ID, or pid © ThoughtWorks 2008
- 12. Concurrency Primitives: spawnA built in function used to create a process. Pid = spawn(Node, Module, Function, Args) © ThoughtWorks 2008
- 13. Another “Unbiased” ComparisonIn Erlang: Pid = spawn(fun() -> io:format(“hello world”) end). In Java: Thread thread = new Thread() { public void run() { System.out.println("Hello World"); } }.start(); © ThoughtWorks 2008
- 14. Concurrency Primitives: send! © ThoughtWorks 2008
- 15. Concurrency Primitives: sendThe send operator passes a message to a process. It is “fire and forget”. Pid ! Msg © ThoughtWorks 2008
- 16. Concurrency Primitives: receivereceive Pattern1 [ when Guard1 ] -> dosomething(). Pattern2 [ when Guard2 ] -> dosomethingelse(). end © ThoughtWorks 2008
- 17. Reliability catch tryMonitor monitor_node(Node, Bool) Unidirectional Link Pid = spawn_link(Node, Module, Fun, Args) Bi-directional © ThoughtWorks 2008
- 18. The Opposite ofRuby © ThoughtWorks 2008 Erlang Ruby Orientation Functional Object Syntax Ugly Beautiful Concurrent Good Bad Track Record Back end Front end Execution Model Compiled Interpreted
- 19. Erlang Servers andFrameworks Mnesia – distributed database YAWS – “yet another web server” ErlyWeb – MVC web framework EUnit Jungerl – third party libraries Perferl ( http://code.google.com/p/perferl ) © ThoughtWorks 2008
- 20. The Erlang ProgrammingLanguage Dennis Byrne - ThoughtWorks [email_address] http://notdennisbyrne.blogspot.com/ © ThoughtWorks 2008