Downloaded 32 times
![ABSTRACIONS EVERYWHERE
The world consists of Lists! => Sequences
• or even lazy Lists! (lazy sequences)
Even Trees and Graphs are lists
Mostly Closuje doesn„t care if it gets
• a List `()
• a Vector []
• a (sorted) (hash) Map {}
• a (sorted) Set #{}](https://image.slidesharecdn.com/funktprog-v-2-0-130215152930-phpapp01/75/Introduction-to-Clojure-and-why-it-s-hot-for-Sart-Ups-27-2048.jpg)
![DRAWBACKS?
• Too many brackets? Random Code from Apache Commons
(defn blank? [s] (every? #(Character/isWhitespace %) s))](https://image.slidesharecdn.com/funktprog-v-2-0-130215152930-phpapp01/75/Introduction-to-Clojure-and-why-it-s-hot-for-Sart-Ups-47-2048.jpg)
![ABSTRACIONS EVERYWHERE
The world consists of Lists! => Sequences
• or even lazy Lists! (lazy sequences)
Even Trees and Graphs are lists
Mostly Closuje doesn„t care if it gets
• a List `()
• a Vector []
• a (sorted) (hash) Map {}
• a (sorted) Set #{}](https://crownmelresort.com/image.slidesharecdn.com/funktprog-v-2-0-130215152930-phpapp01/75/Introduction-to-Clojure-and-why-it-s-hot-for-Sart-Ups-27-2048.jpg)
![DRAWBACKS?
• Too many brackets? Random Code from Apache Commons
(defn blank? [s] (every? #(Character/isWhitespace %) s))](https://crownmelresort.com/image.slidesharecdn.com/funktprog-v-2-0-130215152930-phpapp01/75/Introduction-to-Clojure-and-why-it-s-hot-for-Sart-Ups-47-2048.jpg)
Introduction to Clojure and why it's hot for Sart-Ups
- 2. DISCLAIMER: 1 YOU MIGHTALREADY KNOW! 2 I AM NOT A ‚TYPOLOGIST‘ TAKE IT AS A JOURNEY WITH ANOTHERS EYES
- 3. OVERVIEW • Teil 1:Prolog und Philosophie • Teil 2: Core Language Concepts • Teil 3: (Language Specifics) • Teil 4: Epilog Recently Cedric Beust said something like: „Whenever there is a new paradigm or language learn from it. Don‘t fall in love.“ POLY
- 4. TEIL 1 PROLOGUE &PHILOSOPHY
- 5. MY HISTORY… • 1980-1990 •Prof. Dr. Peter Pepper • Language OPAL • Tutor “Opal is a strongly typed, higher-order, strict, pure functional language, and as such can be classified alongside ML, Haskell, and other modern functional programming languages. However, the language also has a distinctive algebraic flavour in the tradition of languages such as CIP-L, Obj, and others.”
- 6. SCHEME: 1990… Carsten Bormann,Oliver Laumann Scheme, Elk, Emacs Lisp, … imgs.xkcd.com/comics/real_programmers.png
- 7. RESULT LISP
- 8. LUCKY IN MYLITTLE CHESS WORLD… Hence God must be a OO Programmer…
- 9.
- 10.
- 11. complex flow complex state+flow
- 12. INSIGHTS FROM THEPAPER • OOP re-use does rarely work! • komplexity increases exponentiell („boot it…!“) • We „humans“ are not able to master many states Solution: • No State! = No Vars! • less code (e.g. powerful comprehensions) • Higher-Order Functions • everything super abstract
- 13. FIRST LANGUAGE FROMA 3RD PARTY PHILOSOPHY! Together with Scala strong market penetration in Big-Data (Analytics) • BigML • Storm • Cascalog • Nokia • Twitter • Akamai • Factual • Prismatic!! • Groupon • Heroku!! As PaaS! • Top 1 TechRadar von ThoughtWorks (with Scala)
- 14. THOUGHTWORKS RADAR http://thoughtworks.fileburst.com/assets/technology-radar-october-2012.pdf
- 15. CLOJURE TOP #12 1. Functional => pure / first-class / Higher Order Functions 2. Immutable => safe and correct Functions 3. Super Expressiveness => smart with fewer Brackets 4. DSL ready (e.g. parsley) 5. OO or logic concepts easy to integrate (core.logic) 6. Java hosted => fast & libs 7. perfect Java Integration & integration easier then Scala (at least to me) 8. Multicore Ready / multi-CPU with MVCC STM=> always Thread Safe 9. Strong Macros (Scala is currently integrating this) => dream a language 10. dynamic and strong typed (to me d, to vm s) 11. super abstract Programming (composable) 12. Tons of Books, Docs, Links, Videos, Trainings, etc.
- 16. SOME OLD PERFORMANCE NUMBERS=> 24/42 => 57%
- 17. Performance Tipps: - usenative Types & generic collections - use the array wrapper of Clojure - use Java
- 18. LESS CODE = LESS ERRORS Best Expressiveness (rosettacode.org) 73 C# 41 Clojure 115 D 202 Go 68 Groovy 88 Java 26 Prolog .. ups?? (how can this be?) 83 Python 100 Ruby 129 Scala Core logic does it in 33 lines: http://dosync.posterous.com/friendlier-shorter
- 21. NO MUTABLE STATE= NO VARS INPUT files, dbs, user Advantage: Functions can be pure! Disadvantage: sometimes hard
- 22. PART II CORE LANGUAGECONCEPTS
- 23. Neil Ford, Robert„Bob Martin“, Howard Lewis Ship,… „Clojue is a dynamic, strongly typed, functional, high-performance implementation of a lisp on the JVM.“ NF on WJax
- 24. Moving from Syntax… object.methodName(arg2,arg3); methodName(object, arg2, arg3); function(arg1, arg2, arg3); function(arg1 arg2 arg3) (function, arg1, arg2, arg3) to Data Structure! we AST! (function, arg1, arg2, arg3) => :value © Edmund Jackson
- 25. INFINITE ARGS NO OPERATORPRECEDENCE! HOMOICONIC : extend your language! = Metaprogramming! © aphyr.com
- 26. BASIC DATA STRUCTURES © http://codingndesign.com
- 27. ABSTRACIONS EVERYWHERE The worldconsists of Lists! => Sequences • or even lazy Lists! (lazy sequences) Even Trees and Graphs are lists Mostly Closuje doesn„t care if it gets • a List `() • a Vector [] • a (sorted) (hash) Map {} • a (sorted) Set #{}
- 28. DON‘T MIX IDENTITYWITH VALUE! The first ref is a time machine! © http://codingndesign.com
- 29. CEREMONY YIELDS CEREMONY package a.c.b public class Person { public / private / protected vars … private vars … protected vars … constructors … getters / setters … visibility public / private / protected methods … attributes getters setters constructors • All mixed together! namespaces • Leads to more code! methods • Leads to more accidential complexity! and more… • Leads to unneccesary Design Patterns!
- 30. List Map Sequence + A function Set MOSTLY INHERENT COMPLEXITY
- 31. MDD : MAPDRIVEN DESIGN This leads partially to a different design approach: • Identify problem domains • Start with defining your data in terms of maps,lists, seqs,… • The protocol can be the data • Not the API in terms of functions which are already bound to Classes and Types! • Connect these domains loosely by passing data • e.g. with pipes / queues / events / etc. Sam Aaron: „A map key often speaks more and better then a documented interface / class“
- 32. DESIGN PATTERNS VANISH! Peter Norvig demonstrated some time ago http://www.norvig.com/d esign-patterns/ that Lisps in particular either simplify or make invisible most design patterns!
- 33. HIGHER ORDER FUNCTIONS MACROS comp partial, apply map, reduce, sort, filter, super-for, range repear, iterate, drop, cycle interleave, interpose, take, split some?, not-any?, not-every?, … abstract continue for new switch und 1000 mehr assert default if package synchronized boolean do goto private this break double implements protected throw byte else import public throws case enum instanceof return transient catch char extends int final short interface static try void def, if, do, let, ´, fn, loop, recur,… class finally long strictfp volatile const float native super while Lists, Lambda Kalkül Keywords: imparativ
- 34. CONCLUSION PART II •Clojure is a cleaned up lisp • introduction of a sequence abstraction • powered by the JVM • easier symbol resolution / syntax quoting • convenient literal syntax => less parantheses • params in a vector • Commas are whitespaces in data • Avoid many nestings… (cond ((< x 10) „less“) (cond (< x 10) „less“ (> x 10) „more“)) (> x 10) „more“)
- 35. PART III LANGUAGE SPECIFICS PEEK IN…
- 36. CLOJURE AREAS Datatypes Functions map, reduce, Java Interop pmap Control Sequences / sequable map / reduce / reduce++ Laziness Concurrency / Reference Types (STM) Uses fork / join for easy seq processing on all Datatypes & Protocols cores you have. Multimethods Macros
- 37. MAPS ARE FUNCTIONS KEYSARE FUNCTIONS * IS A FUNCTION > (def edlich {:name „edlich“ :age 42}) > (edlich :age) => 42 > (:age edlich) => 42
- 38. HAMMOCK DRIVEN DEVELOPMENT- HDD http://blip.tv/clojure/hammock-driven-development-4475586 Don„t move your fingers fast… Think & Sleep!
- 39. 4CLOJURE • Not acompetition about the shortest unreadable code • but shorter code! • more consise code! • craftable code! „there is a simpler solution“ • more abstract code! see http://tapestryjava.blogspot.de/2013/02/crafting-code-in-clojure.html
- 42.
- 43. TONS OF MAGIC…PIPES! or let for even more readability
- 44. BETTER REPL THEN* Always run & change your env...! No interpretation. Recompile & run in no time. Idea: Bret Victor “Inventing on Principle” http://www.youtube.com/watch?v=PUv66718DII
- 45. FOR / LOOPS= A CODE SMELL! Do a recursive reverse withouth ‚reverse„ 95% no loop needed!
- 46. WHY GOOD 4STARTUPS • Truly Composable • Fast • Correct • Concurrent Access Solved: Atoms, Refs & Agents (Actors e.g. via Akka) • Multicore: • Lazy Sequences / Caching / Old Reducers • New Reducers fold combine fork . . . join } like Map / Reduce split and calc on N cores
- 47. DRAWBACKS? • Too many brackets? Random Code from Apache Commons (defn blank? [s] (every? #(Character/isWhitespace %) s))
- 48. DRAWBACKS? • Eclipse, IntelliJ, NetBeans, IDEs are good but far from JavaIDEs • Many reasons for a IDE vanish (lucky with emacs, vim, sublimetext) • Debugging is not mature • visual VM is ok. By the way we do not debug state! • We copy snippet in REPL and have the solution! • Static is more safe? Type mismatch is rare • Leiningen Build 2.0 is ok (uses Maven internally and feels like Maven) • List add Back, Vector add front => because… • Don„t mix abstract and concrete world • Namespaces are hard • But super powerful…
- 49. THEN WHEN HAVINGA BEER HE TOLD ME: „Well since 2010 I am working on a database!“ ...whow
- 50. DATOMIC ! Could bethe next talk! © Datomic
- 51. STEFAN KAMPHAUSEN Chapter 1.3 EinWort der Warnung ist angebracht. Die Benutzung von Lisp- artigen Programmiersprachen kann süchtig machen und / oder die Entwicklung mit anderen Sprachen unangenehm bis schmerzhaft erscheinen lassen. Sollten Sie sich nach der Lektüre dieses Buches und ggf. einiger Projekte nicht mehr in der Lage sehen, mit anderen Sprachen zu arbeiten, können wir dafür keine Verantwortung übernehmen.“ (It‘s time for a warning. The usage of Lisp-alike languages can lead to addiction. The usage of other language then becomes awkward and painful. We can not take any responsibility if you – after reading this book – become unable to work with other languages!)
- 52. QUOTES… „Clojure does notfeel like hacking. It feels like a very analytical precision surgery of a problem into its component parts. You can write big, ugly Clojure. But good Clojure is readable and maintainable, and a pleasure to write in.” Eric Normand “If you try to build abstractions in Java code it tends to get bigger. If you write abstract code in Clojure it tends to get shorter.” “The other day, I was working on a little bit of code in Clojure, just touching up some exception reporting, when I was suddenly struck by one of the fundamental reasons that Clojure is so enjoyable to code in. Clojure is craftable: that is, in Clojure you have the option to craft at your code to make it more concise, easier to read, and easier to maintain. That is not the case for all, or perhaps even most, programming languages.” Howard Lewis Ship (Tapestry) http://tapestryjava.blogspot.de/2013/02/crafting-code-in-clojure.html and others converted as Uncle ‚Bob‘ Martin, Neil Ford, etc…
- 53.