Clojure all the way down: Finally a useful LISP

http://bucharestfp.ro/2015/10/21/clojure-all-the-way-down-finally-a-useful-lisp/

Transcript

1. @ArgesRic
   CLOJURE ALL THE WAY DOWN
   Ricardo J. Méndez
   

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2. @ArgesRic
   WHO AM I?
   • Ricardo J. Méndez
   
   • Entrepreneur, founder, Numergent
   
   • Clojure articles at http://numergent.com/articles/
   
   • Twitter: @ArgesRic
   

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3. @ArgesRic
   WHAT DO I DO?
   • CTO for hire running projects for large companies
   
   • Working on our own projects (open source and otherwise)
   
   • Previously:
   
   • Data analysis for banking, healthcare
   
   • Game development
   

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4. @ArgesRic
   HOW DID WE GET TO CLOJURE?
   • First encountered LISP over 20 years ago
   
   • Genetic programming!
   
   • Fascinated with the language…
   
   • Limited tooling and libraries.
   

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5. @ArgesRic
   HOW DID WE GET TO CLOJURE?
   • It was different.
   
   • Had access to the full Java platform…
   
   • …while still giving you a fully functional approach.
   
   • New paradigms shake up your thought process.
   

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6. @ArgesRic
   OTHER OPTIONS?
   (Event though it aims to solve the same problems as Clojure)
   

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7. @ArgesRic
   WHAT WE’LL TALK ABOUT
   • Not a language intro.
   
   • For a great one, see Rich Hickey’s “Clojure, Made Simple” https://
   www.youtube.com/watch?v=VSdnJDO-xdg
   
   • Focus on how design decisions affect your work.
   
   • Won’t be overloaded with code samples.
   

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8. @ArgesRic
   BIASES
   • Somewhat personal talk - will focus on why it works for me.
   
   • I’ve always found the elegance of LISPs appealing.
   
   • SPOILER ALERT: Unapologetically positive about it…
   
   • … so we’ll start with the scary bits.
   

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9. @ArgesRic
   THE SCARY BITS
   

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10. @ArgesRic
    IT WILL SEEM WEIRD
    

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11. @ArgesRic
    IT WILL SEEM WEIRD
    • Not because of grammar…
    
    • Not because it’s a different vocabulary…
    
    • But because it has different semantics.
    

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12. @ArgesRic
    … BECAUSE OF ITS SEMANTICS
    • Clojure doesn’t just use different words,
    
    • Clojure’s mechanism for making meaning is different.
    

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13. @ArgesRic
    … BECAUSE OF THE PROBLEMS IT
    SOLVES
    “We can't solve problems by using the same kind of
    thinking we used when we created them.”
    
    — Albert Einstein
    (Totally not an appeal to unrelated authority)
    

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14. @ArgesRic
    … WHICH ARE…
    • Mutability
    
    • Inconsistency
    
    • Massive syntax
    

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15. @ArgesRic
    DOCUMENTATION
    into
    (into to from) (into to xform from)
    
    Returns a new coll consisting of to-coll with all of the
    items of from-coll conjoined. A transducer may be
    supplied.
    

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16. @ArgesRic
    DOCUMENTATION
    

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17. @ArgesRic
    DOCUMENTATION
    “the site is fucking useless, its more confusing than
    helpful”
    
    — Radu
    (Related authority on the learning curve)
    

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18. @ArgesRic
    DOCUMENTATION
    • Doesn’t tell you that you can ignore transducers for now.
    
    • Doesn’t tell you that there’s a conj verb.
    
    • Doesn’t tell you anything else that might help a newbie.
    

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19. @ArgesRic
    DOCUMENTATION
    • It's going to take one collection, and move it into a different collection by
    conjoining items to it.
    
    • Why conjoining?
    
    • conjoin as a verb has a specific meaning in Clojure.
    

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20. @ArgesRic
    DOCUMENTATION, FULL OF EXAMPLES
    

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21. @ArgesRic
    THEM’S THE SCARY BITS
    

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22. @ArgesRic
    PROBLEMS THAT CLOJURE SOLVES
    

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23. @ArgesRic
    SOLVING…
    • Mutability
    
    • Inconsistency
    
    • Massive syntax
    

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24. @ArgesRic
    IMMUTABILITY AND FUNCTIONAL
    PROGRAMMING
    Show of hands… how many are doing functional
    programming?
    

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25. @ArgesRic
    IMMUTABILITY AND FUNCTIONAL
    PROGRAMMING
    • Functions are not methods by a different name.
    
    • Take values, returns a value…
    
    • … but doesn’t change anything in the middle.
    

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26. @ArgesRic
    IMMUTABILITY AND FUNCTIONAL
    PROGRAMMING
    • C# has LINQ, which sorta gets you there…
    
    • Java is finally catching up…
    
    • … but neither enforces immutability.
    
    • You’re still juggling objects. Some will methods will change properties.
    

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27. @ArgesRic
    IMMUTABILITY AND FUNCTIONAL
    PROGRAMMING
    • That’s fine when you have a couple classes.
    
    • Maybe you can keep the side effects in mind as you code.
    
    • Maybe you know what that ProcessTransactions() returns a value, but
    changes a couple of things…
    
    • … but we are fallible, with finite mindspace.
    

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28. @ArgesRic
    IMMUTABILITY AND FUNCTIONAL
    PROGRAMMING
    

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29. @ArgesRic
    IMMUTABILITY AND FUNCTIONAL
    PROGRAMMING
    

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30. @ArgesRic
    IMMUTABILITY AND FUNCTIONAL
    PROGRAMMING
    Even assuming you can keep all those side effects in
    mind…
    
    why would you want to?
    

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31. @ArgesRic
    IMMUTABILITY AND FUNCTIONAL
    PROGRAMMING
    

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32. @ArgesRic
    IMMUTABILITY AND PARALLELISM
    • Immutability makes parallelism much simpler.
    
    • Look ma, no locks!
    
    • You don’t care where it runs, since nobody will modify the data.
    
    • Had to do parallelism by hand before. Never going back.
    

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33. @ArgesRic
    MASSIVE SYNTAX
    • Bigger problem than unfamiliar semantics.
    
    • You only need to learn semantics once, syntax is an on-going cost.
    
    • Again… it uses up headspace.
    
    • Would you rather use it for the syntax, or for the concepts?
    

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34. @ArgesRic
    MASSIVE SYNTAX
    

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35. @ArgesRic
    MASSIVE SYNTAX
    • Code is read more than it is written.
    
    • We need to convey meaning quickly, without unnecessary ceremony…
    
    • Doesn’t matter if it’s a new programmer, or you six months after you
    wrote it.
    
    • And that’s before we discuss the baroque class architectures people
    build on top.
    

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36. @ArgesRic
    INCONSISTENCY
    • You need to experience it.
    
    • Clojure thinks in terms of collections and encourages you to use
    maps.
    
    • Same functions act over everything. Even records are map-like.
    

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37. @ArgesRic
    THE LEARNING PROCESS
    

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38. @ArgesRic
    NATURAL LANGUAGES
    • English: Trivial grammar, pronunciation is a mess.
    
    • Spanish: straightforward, clean, pronunciation; grammar is more
    elaborate than English.
    
    • Romanian: …
    

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39. @ArgesRic
    CLOJURE GRAMMAR
    • Weight is on the verbs.
    
    • Verb goes first.
    
    • Verb is followed by anything it acts upon.
    

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40. @ArgesRic
    CLOJURE GRAMMAR
    (+ 1 2 3 4)
    
    (map :val [{:id 1 :val "a"} {:id 2 :val "b"} {:id 3 :val "something else”}])
    
    (auth/create-auth-token (:username content) (:password
    content))
    

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41. @ArgesRic
    CLOJURE GRAMMAR
    (+ 1 2 3 4)
    
    (map :val [{:id 1 :val "a"} {:id 2 :val "b"} {:id 3 :val "something else”}])
    
    (auth/create-auth-token (:username content) (:password
    content))
    

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42. @ArgesRic
    MIND THE SEMANTICS, THOUGH
    • It’s not about learning a new function now and then.
    
    • You have to use it to get acquainted with the semantics.
    
    • Need to learn how to express yourself differently.
    
    • It’s not about understanding the language, it’s about grokking its
    semantics.
    

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43. @ArgesRic
    MIND THE SEMANTICS, THOUGH
    grok:
    
    “to understand so thoroughly that the observer
    becomes a part of the observed”
    
    — Robert Heinlein, Stranger in a Strange Land
    

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44. @ArgesRic
    IT’S ABOUT DOING
    You can’t just subscribe to a running magazine, you
    have to get out there and run.
    4Clojure.com is your friend.
    

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45. @ArgesRic
    LEARNING CURVE
    “I am to going to fetch the value..”
    

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46. @ArgesRic
    LEARNING CURVE
    “I am to going to fetch the value..”
    They’re trying to hang the mental constructs of their
    much more complex first language onto the
    simplicity of English grammar.
    

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47. @ArgesRic
    LEARNING CURVE
    The tricky thing about Clojure’s grammar is that it’s
    much simpler than you expect.
    

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48. @ArgesRic
    LEARNING CURVE
    • Most of my time goes to figuring out what I want to say.
    
    • In C# or Java, I spent a lot of time in scaffolding and ceremony before
    getting to that.
    
    • There’s no boilerplate. It’s just you and what you want to calculate.
    

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49. @ArgesRic
    BOOKS
    Daniel Higginbotham, Clojure for the
    Brave and True
    
    

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50. @ArgesRic
    BOOKS
    Dmitri Sotnikov, Web Development
    with Clojure
    
    

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51. @ArgesRic
    THE CLOJURE WAY
    

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52. @ArgesRic
    THE CLOJURE WAY
    • Small, focused, easily replaceable libraries
    
    • Templates over frameworks. See Luminus (http://
    www.luminusweb.net/)
    
    • No automagic
    

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53. @ArgesRic
    NO AUTOMAGIC
    • No method injection… since we don’t even have objects.
    
    • I used to love Grails’ approach… until I realized I couldn’t control it.
    
    • Full control over what’s going on.
    
    • Libraries are easy to replace, since you don’t have to wonder about
    what goes on behind the scenes.
    

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54. @ArgesRic
    CLOJURE ALL THE WAY DOWN
    

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55. @ArgesRic
    REFACTORING - CLOJURE, REVISITED
    • Immutability helps with refactoring.
    
    • Code is trivial to manipulate, since…
    
    • … it’s a tree structure
    
    • … you don’t need to worry about context.
    

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56. @ArgesRic
    REFACTORING - CLOJURE, REVISITED
    • Yes, code is read more than it is written…
    
    • … but writing is rewriting.
    
    • We will not get it perfect the first time.
    

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57. @ArgesRic
    REPL - CLOJURE, WHILE EXPLORING
    

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58. @ArgesRic
    REPL - CLOJURE, WHILE EXPLORING
    • Trivial use of your functions as you develop.
    
    • Excellent for exploring someone else’s functions (remember, no
    context!)
    
    • I’ve found myself experimenting with my new functions on the REPL,
    then codifying those as tests.
    

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59. @ArgesRic
    CLOJURESCRIPT - CLOJURE, 

    ON THE BROWSER
    • Gets transpiled to Javascript.
    
    • All of Clojure’s advantages, on the browser.
    
    • Straightforward and consistent.
    
    • Both front and backend on the same code.
    
    • Enables some amazing tools.
    

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60. @ArgesRic
    CLOJURESCRIPT COMPONENTS:

    REAGENT
    • React wrapper: https://reagent-project.github.io/
    
    • Clean, straightforward, excellent examples.
    

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61. @ArgesRic
    CLOJURESCRIPT, REACTIVE:

    RE-FRAME
    • Reactive pattern using Reagent
    
    • https://github.com/Day8/re-frame
    
    • Tiny surface area affected when modifying front end code.
    

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62. @ArgesRic
    CLOJURESCRIPT, RELOADED:

    FIGWHEEL
    • Created by Bruce Hauman
    
    • https://github.com/bhauman/lein-figwheel
    
    • Scans ClojureScript source folders, reloads the application live.
    
    • “Presses F5 for you, big whoop”
    
    • No data loss.
    

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63. @ArgesRic
    FINAL SUGGESTIONS
    

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64. @ArgesRic
    FINAL SUGGESTIONS
    • Start off small. Unlike going from C# to Java, it’s not just about learning new
    vocabulary.
    
    • There will be a learning curve.
    
    • Don’t get too used to blindly hack off templates at first just because you want
    to start big.
    
    • 5 mistakes Clojure newbies make: http://adambard.com/blog/five-mistakes-
    clojure-newbies-make/
    

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65. @ArgesRic
    QUESTIONS?
    

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66. @ArgesRic
    THANKS!
    

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