Reading Clojure

Reading Clojure Ricardo J. Méndez [email protected] @ArgesRic  https://mastodon.social/@ricardojmendez

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

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

@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?

@ArgesRic This one’s for the ﬁrst two.

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

@ArgesRic I bollocksed up the ﬁrst two.

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

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

@ArgesRic

@ArgesRic Let’s describe how we see this.

@ArgesRic

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

@ArgesRic

@ArgesRic So let’s dissect things a bit.

@ArgesRic (1 2 3)   [1 2 3]  (+ 1
2 3)  [+ 1 2 3]

@ArgesRic Evaluation semantics

@ArgesRic (+ 1 2 3)   (1 2 3)

@ArgesRic Trick question!

@ArgesRic (+ 1 2 3)   (1 2 3)

@ArgesRic We can always quote a list.

@ArgesRic If you’re joining us from Java… Or C#…  
  Or not-a-LISP...

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

@ArgesRic *except all those special cases…

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

@ArgesRic A special form aside…

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

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

@ArgesRic Primitives are so rare they are special.

@ArgesRic Back to the if

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

@ArgesRic “Branches, in parenthesis"

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

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

@ArgesRic Back to defn

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

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

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

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

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

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

@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 )

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

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

@ArgesRic Everything will follow this exact same pattern.

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

@ArgesRic Let’s break some stuﬀ!

@ArgesRic (inc) (inc 1) (inc inc)

@ArgesRic inc [inc] [inc 1] [inc 1 inc]

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

@ArgesRic Abusing the syntax to disabuse you of misconceptions.

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

@ArgesRic (apply + [1 2 3 4])  (get {+ 1
- 2 * 3} -)

@ArgesRic … we’re about out of time

@ArgesRic Thank you! Ricardo J. Méndez [email protected] @ArgesRic https://mastodon.social/@ricardojmendez https://numergent.com/talks/

Reading Clojure

Reading Clojure

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