Reading Clojure

If there's one thing that trips Clojure newcomers is how to read the damned thing.

Clojure's syntax is very simple, and yet newcomers to Clojure tend to project into the language the complexity of other languages they're used to. We'll go through a few Clojure examples and deconstruct them to show how there's even less syntax to it than you probably think.

Video: https://youtu.be/t_T5wtLyZos

Transcript

1. Reading Clojure
   Ricardo J. Méndez
   ricardo@numergent.com
   @ArgesRic

   https://mastodon.social/@ricardojmendez
   

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2. @ArgesRic
   This is about the thought
   process when evaluating things.
   

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3. @ArgesRic
   “What in the name of Cthulhu’s
   green tentacles did I commit to?”
   

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4. @ArgesRic
   Show of hands
   • Who here isn't programming in Clojure yet?
   • Who is kind of familiar with the language but still finding their
   footing?
   • Who considers themselves to be fully comfortable in it?
   

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5. @ArgesRic
   This one’s for the first two.
   

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6. @ArgesRic
   Learning stages
   • First we learn by reading;
   • Then we learn by imitating;
   • And finally, we learn by creating.
   

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7. @ArgesRic
   I bollocksed up the first two.
   

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8. @ArgesRic
   Clojure can be hard to read
   because of how simple it is.
   

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9. @ArgesRic
   Syntax is that part of the
   language that’s set in stone.
   

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10. @ArgesRic
    

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11. @ArgesRic
    Let’s describe how we see this.
    

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12. @ArgesRic
    

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13. @ArgesRic
    

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14. @ArgesRic
    Tokens are the wrong way of
    thinking about Clojure.
    

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15. @ArgesRic
    

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16. @ArgesRic
    So let’s dissect things a bit.
    

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17. @ArgesRic
    (1 2 3)
    

    [1 2 3]

    (+ 1 2 3)

    [+ 1 2 3]
    

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18. @ArgesRic
    Evaluation semantics
    

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19. @ArgesRic
    (+ 1 2 3)
    

    (1 2 3)
    

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20. @ArgesRic
    Trick question!
    

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21. @ArgesRic
    (+ 1 2 3)
    

    (1 2 3)
    

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22. @ArgesRic
    We can always quote a list.
    

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23. @ArgesRic
    If you’re joining us from
    Java… Or C#… 

    

    Or not-a-LISP...
    

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24. @ArgesRic
    “Yeah, yeah, homoiconicity, we
    get it”
    

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25. @ArgesRic
    *except all those special
    cases…
    

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26. @ArgesRic
    (if odd?
    (do-something [1 3 5 7])
    (do-another-thing [0 2 4 6]))
    

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27. @ArgesRic
    (if odd?
    (do-something [1 3 5 7])
    (do-another-thing [0 2 4 6]))
    

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28. @ArgesRic
    (if odd?
    (do-something [1 3 5 7])
    (do-another-thing [0 2 4 6]))
    

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29. @ArgesRic
    A special form aside…
    

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30. @ArgesRic
    “That’s the stuff that’s
    different!”
    

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31. @ArgesRic
    They aren’t special cases.
    They are primitives.
    

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32. @ArgesRic
    Primitives are so rare they are
    special.
    

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33. @ArgesRic
    Back to the if
    

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34. @ArgesRic
    (if odd?
    (do-something [1 3 5 7])
    (do-another-thing [0 2 4 6]))
    

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35. @ArgesRic
    (if odd?
    (do-something [1 3 5 7])
    (do-another-thing [0 2 4 6]))
    

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36. @ArgesRic
    (if odd?
    (do-something [1 3 5 7])
    (do-another-thing [0 2 4 6]))
    

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37. @ArgesRic
    (if odd?
    (do-something [1 3 5 7])
    (do-another-thing [0 2 4 6]))
    

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38. @ArgesRic
    “Branches, in parenthesis"
    

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39. @ArgesRic
    (if got-a-list?
    (convert-to-string [1 3 5 7])
    "Got something else")
    

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40. @ArgesRic
    We are always evaluating.
    Stop thinking on terms of
    “execution”.
    

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41. @ArgesRic
    Back to defn
    

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42. @ArgesRic
    (defn plus-one [v w]
    (+ w v 1))
    

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43. @ArgesRic
    (
    defn ; We are evaluating this
    plus-one
    [v w]
    (+ w v 1)
    )
    

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44. @ArgesRic
    (
    defn
    plus-one ; All these
    [v w] ; are
    (+ w v 1) ; parameters.
    )
    

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45. @ArgesRic
    (
    defn
    plus-one ; This is an identifier
    [v w]
    (+ w v 1)
    )
    

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46. @ArgesRic
    (
    defn
    plus-one
    [v w] ; This is a vector w/param ids
    (+ w v 1)
    )
    

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47. @ArgesRic
    (
    defn
    plus-one
    [v w]
    (+ w v 1) ; This is a list to evaluate
    )
    

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48. @ArgesRic
    (
    defn ; We are invoking this
    plus-one ; This is an identifier
    [v w] ; This is a vector w/param ids
    (+ w v 1) ; This is a list to evaluate
    )
    

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49. @ArgesRic
    (defn get-from-string
    [conn long-url]
    (let [url (db/get-url conn long-url)
    parsed (db/parse url)]
    (clean-up parsed)))
    

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50. @ArgesRic
    (
    defn
    get-from-string
    [conn long-url]
    (
    let
    [url (db/get-url conn long-url) parsed (db/parse url)]
    (clean-up parsed)
    )
    )
    

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51. @ArgesRic
    (
    defn
    get-from-string
    [conn long-url]
    (
    let
    [url (db/get-url conn long-url) parsed (db/parse url)]
    (clean-up parsed)
    )
    )
    

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52. @ArgesRic
    (
    defn
    get-from-string
    [conn long-url]
    (
    let
    [url (db/get-url conn long-url) parsed (db/parse url)]
    (clean-up parsed)
    )
    )
    

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53. @ArgesRic
    (
    defn
    get-from-string
    [conn long-url]
    (
    let
    [url (db/get-url conn long-url) parsed (db/parse url)]
    (clean-up parsed)
    )
    )
    

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54. @ArgesRic
    Everything will follow this exact
    same pattern.
    

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55. @ArgesRic
    The Tao of Clojure:
    There is nothing but the list.
    

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56. @ArgesRic
    Let’s break some stuff!
    

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57. @ArgesRic
    (inc)
    (inc 1)
    (inc inc)
    

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58. @ArgesRic
    inc
    [inc]
    [inc 1]
    [inc 1 inc]
    

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59. @ArgesRic
    (defn a-function [v]
    [+ 1 2 3 4 5]
    (plus-one 2 3)
    plus-one [inc]
    [inc 1]
    v)
    

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60. @ArgesRic
    (defn a-function [v]
    [+ 1 2 3 4 5]
    (plus-one 2 3)
    plus-one
    [inc]
    [inc 1]
    v)
    

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61. @ArgesRic
    Abusing the syntax to disabuse
    you of misconceptions.
    

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62. @ArgesRic
    #1: "Everything needs to be
    wrapped in parenthesis."
    #2: "There’s all these special
    cases."
    

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63. @ArgesRic
    (apply + [1 2 3 4])

    (get {+ 1 - 2 * 3} -)
    

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64. @ArgesRic
    … we’re about out of time
    

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65. @ArgesRic
    Thank you!
    Ricardo J. Méndez
    ricardo@numergent.com
    @ArgesRic
    https://mastodon.social/@ricardojmendez
    https://numergent.com/talks/
    

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