Munich Clojure Workshop - 06 - Destructuring

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Transcript

1. Destructuring Friday, October 11, 13
2. Apart from simple types, there are collections, which contain other things. Friday, October 11, 13
3. But sometimes we want simple data out of a collection type. Friday, October 11, 13
4. Actually, quite often. Friday, October 11, 13
5. (def my-collection [1 2 [3 4] 5]) (first my-collection) ;=> 1 (nth my-collection 2) ;=> [3 4] Friday, October 11, 13
6. It takes a function(+) and some arguments(1) and returns a closure with the arguments pre-set. But if we want multiple elements, this gets ugly fast: (let [a (nth my-collection 0) b (nth my-collection 1) c (nth my-collection 2) d (nth my-collection 3)] (println a c)) Friday, October 11, 13
7. How many of you know Python? Friday, October 11, 13
8. How many of you know Python? a, b, c, d = my_collection Friday, October 11, 13
9. We want this too! Friday, October 11, 13
10. Hey, we can do this too! (let [[a b c d] my-collection] (println a c)) Friday, October 11, 13
11. What about this? a, b, *more = my_collection Friday, October 11, 13
12. Can do! (let [[a b & more] my-collection] (println a more)) Friday, October 11, 13
13. But wait, it's not only vectors! (def my-map {:lang "Clojure" :platform "JVM" :version "1.5.1"}) (let [{language :lang} my-map] (println language)) Friday, October 11, 13
14. Sothere is some kind of"unpacking language"? Friday, October 11, 13
15. Sothere is some kind of"unpacking language"? YEPa This is called destructuring. Friday, October 11, 13
16. What else? • You can use this language in binding forms • So, not only let but also fn/defn • It works recursively • More hands-on stuff in the exercises Friday, October 11, 13