Programming across paradigms

Presented at PolyConf 2017: https://polyconf.com/

The programming paradigm we work in shapes every aspect of how we craft our code, providing a model of what a program is, and what it can and should be. In this talk, we’ll explore the connections between the programs we write, the languages we work in, and the paradigms we use, and try to get some historical and philosophical perspective on the familiar paradigms of imperative, declarative, object-oriented, and functional programming, focusing on the points where they intersect and collide. We’ll discover the valuable lessons different paradigms can teach us, and find motivation to stop arguing with our fellow coders about which is superior, and instead encourage each other - as individuals and a community - to pursue poly-paradigm programming.

Transcript

1. programming across
   paradigms
   @AnjanaVakil
   PolyConf 2017
   

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2. hi, I’m @AnjanaVakil!
   The
   Recurse
   Center
   

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3. 1978 ACM Turing Award Lecture
   

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4. “I believe the best chance we have to
   improve the general practice of
   programming is to attend to our paradigms.”
   Robert W. Floyd
   “The paradigms of programming.”, 1979. p. 456
   

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5. what is a
   paradigm?
   

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6. Front cover of 1st edition paperback (1962), via Wikimedia
   

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7. a paradigm is a worldview
   

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8. a paradigm is a model
   

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9. “All models are wrong”
   George E. P. Box
   "Robustness in the strategy of scientific model building", 1979, p. 202.
   

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10. “In learning a paradigm the scientist
    acquires theory, methods, and
    standards together, usually in an
    inextricable mixture.”
    Thomas S. Kuhn
    The Structure of Scientific Revolutions, (2nd ed.) 1970. p. 109.
    

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11. theory
    what entities make up the universe
    how they behave and interact
    

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12. methods & standards
    which problems are worth solving
    which solutions are legitimate
    

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13. a paradigm enables progress
    

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15. paradigm
    

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16. Scenography of the Ptolemaic cosmography by Loon, J. van (Johannes), ca. 1611–1686. via Wikimedia
    

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17. paradigm
    anomaly
    

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18. paradigm
    anomaly
    crisis
    

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19. paradigm
    anomaly
    crisis
    shift
    

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20. Scenographia Systematis Copernicani (The Copernican System), 1686. via Wikimedia
    

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21. paradigm
    anomaly
    crisis
    shift
    

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22. what is
    programming?
    

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24. imperative
    programming
    follow my
    commands
    in the order I
    give them
    remember state
    

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25. imperative
    programming
    “Clocks Gears Wallpaper” via Wallpoper
    

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26. object-oriented
    programming
    keep your state
    to yourself
    receive my
    messages
    respond as you
    see fit
    

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27. object-oriented
    programming
    “Slide of the Week: Increased WBC, April 14, 2011” via Center for Genomic Pathology
    

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28. functional
    programming
    mutable state is
    dangerous
    pure functions
    are safe
    data goes in
    data comes out
    

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29. functional
    programming
    “2012 Chevrolet Cruze on the production line at Lordstown Assembly in Lordstown, Ohio” via GM
    

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30. declarative
    programming
    these are the
    facts
    this is what i
    want
    i don’t care how
    you do it
    

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31. declarative
    programming
    “Sudoku05” by Jelte (CC BY-SA 3.0) via Wikimedia
    

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32. https://www.info.ucl.ac.be/~pvr/paradigms.html
    

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33. are they really
    so different?
    

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34. shared
    mutable state
    

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35. shared
    mutable state
    

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36. shared
    mutable state
    

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37. shared
    mutable state
    

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38. “I'm sorry that I long ago coined the
    term "objects" for this topic because it
    gets many people to focus on the lesser
    idea. The big idea is "messaging".”
    Alan Kay
    Message to Smalltalk/Squeak mailing list, 1998
    

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39. message
    ↓
    response
    

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40. input
    ↓
    output
    

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41. behavior
    

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42. Lambda calculus
    TRUE := λx.λy.x
    FALSE := λx.λy.y
    Smalltalk
    class True
    ifTrue: a ifFalse: b
    ^ a value
    class False
    ifTrue: a ifFalse: b
    ^ b value
    

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43. which paradigm is
    The Best?
    

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44. “All models are wrong…
    George E. P. Box
    "Robustness in the strategy of scientific model building", 1979, p. 202.
    

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45. “All models are wrong
    but some are useful”
    George E. P. Box
    "Robustness in the strategy of scientific model building", 1979, p. 202.
    

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47. “Is the model true?”
    “Is the model illuminating and useful?”
    George E. P. Box
    "Robustness in the strategy of scientific model building", 1979, p. 202.
    

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48. what can a paradigm
    illuminate?
    

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49. be explicit
    focus on implementation
    be machine-efficient
    

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50. Rust for Elixir: NIFty!
    #[macro_use] extern crate rustler;
    #[macro_use] extern crate rustler_codegen;
    #[macro_use] extern crate lazy_static;
    use rustler::{NifEnv, NifTerm, NifResult, NifEncoder};
    mod atoms { rustler_atoms! { atom ok; } }
    rustler_export_nifs! { "Elixir.Testing.MyNif", [("add", 2, add)], None }
    fn add(env: NifEnv, args: &[NifTerm]) -> NifResult> {
    let num1: i64 = args[0].decode()?;
    let num2: i64 = args[1].decode()?;
    // complicated math here
    // such imperative, so performance, wow
    Ok((atoms::ok(), result).encode(env))
    }
    Adapted from H.E.B. Josephsen, “Elixir FFI with Rust”, PolyConf 2017.
    

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51. be abstract
    focus on domain
    be human-efficient
    

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52. Embedded DSL in Java
    cal = new Calendar();
    cal.event("PolyConf")
    .on(2017, 07, 09)
    .from("09:00")
    .to("19:00")
    .at("La Géode");
    Adapted from M. Fowler & R. Parsons, Domain Specific Languages, 2011, p. 345.
    

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53. encapsulate
    remember
    

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54. Context-aware API in F#
    module MyApi =
    let fnA dep1 dep2 dep3 arg1 = doAWith dep1 dep2 dep3 arg1
    let fnB dep1 dep2 dep3 arg2 = doBWith dep1 dep2 dep3 arg2
    type MyParametricApi(dep1, dep2, dep3) =
    member __.FnA arg1 = doAWith dep1 dep2 dep3 arg1
    member __.FnB arg2 = doBWith dep1 dep2 dep3 arg2
    Adapted from E. Tsarpalis, “Why OOP Matters (in F#)”, 2017.
    

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55. isolate
    transform
    

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56. Adapted from J. Kerr, “Why Functional Matters: Your white board will never be the same”, 2012.
    Functional program flow
    

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57. Each paradigm supports a set of
    concepts that makes it the best
    for a certain kind of problem.
    Peter Van Roy
    “Programming paradigms for dummies: What every programmer should know”, 2009, p. 10.
    

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58. no paradigm is best absolutely
    each is best for a certain case
    

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59. multi-paradigm languages
    give you options
    

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60. what’s the
    point?
    

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61. paradigms enable programming
    

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62. paradigms define programming
    

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63. embrace your paradigm,
    don’t fight it
    

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64. be open to shift
    

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65. “If the advancement of the general art of
    programming requires the continuing
    invention and elaboration of paradigms...”
    Robert W. Floyd
    “The paradigms of programming.”, 1979. p. 456
    

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66. “... advancement of the art of the
    individual programmer requires that
    [t]he[y] expand [their] repertory of
    paradigms.”
    Robert W. Floyd
    “The paradigms of programming.”, 1979. p. 456
    

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67. learn new paradigms
    invent new paradigms
    

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68. let’s attend to our paradigms
    

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69. David Albert, Darius Bacon, Julia Evans
    & the Recurse Center
    PolyConf organizers
    thank you!
    @AnjanaVakil
    

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70. References & further reading/watching
    Box, George E.P. (1979), "Robustness in the strategy of scientific model building", in Launer & Wilkinson, Robustness in Statistics, Academic Press, pp. 201–236.
    Cook, William (2012). “A Proposal for Simplified, Modern Definitions of ‘Object’ and ‘Object Oriented’”. wcook.blogspot.fr/2012/07/proposal-for-simplified-modern.html
    Floyd, Robert W. (1979). “The paradigms of programming.” Commun. ACM 22, 8, 455-460.
    Fowler, Martin, with Parsons, Rebecca. (2011). Domain Specific Languages. Addison-Wesley.
    Josephsen, Hans Elias Bukholm (2017). “Elixir FFI with Rust”, PolyConf. http://slides.com/hansihe/rustler#/
    Kay, Alan (1998). Message to Smalltalk/Squeak mailing list. wiki.c2.com/?AlanKayOnMessaging
    Kerr, Jessica (2012). “Why Functional Matters: Your white board will never be the same”. blog.jessitron.com/2012/06/why-functional-matters-your-white-board.html
    Kerr, Jessica (2014). “Functional Principles for Object-Oriented Development”, GOTO Chicago. https://youtu.be/GpXsQ-NIKXY
    Kuhn, Thomas S. (1970). The Structure of Scientific Revolutions. (2nd ed.). University of Chicago Press.
    Tsarpalis, Eirik. (2017). “Why OO matters (in F#)”. https://eiriktsarpalis.wordpress.com/2017/03/20/why-oo-matters-in-f/
    Van Roy, Peter. (2009). “Programming paradigms for dummies: What every programmer should know.” In New computational paradigms for computer music, p. 104.
    Williams, Ashley. (2015). “If you wish to learn ES6/2015 from scratch, you must first invent the universe”, JSConf. https://youtu.be/DN4yLZB1vUQ
    

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