![(defn concat [xs ys]!
(if (empty? xs)!
ys!
(let [[h & t] xs]!
(cons h (concat t ys)))))
Lots of Irritating Stupid Parentheses](https://image.slidesharecdn.com/clojure-fromgroundup-150908064630-lva1-app6891/85/Clojure-from-ground-up-4-320.jpg)
![(defn concat [xs ys]!
(if (empty? xs)!
ys!
(let [[h & t] xs]!
(cons h (concat t ys)))))
LISt Processing](https://image.slidesharecdn.com/clojure-fromgroundup-150908064630-lva1-app6891/85/Clojure-from-ground-up-5-320.jpg)
![Functional Programming
• function as first-class citizen
• work by arguments and returning value
(defn make-adder [base]
(let [ref (atom base)]
(fn [delta]
(swap! ref (partial + delta)))))](https://image.slidesharecdn.com/clojure-fromgroundup-150908064630-lva1-app6891/85/Clojure-from-ground-up-9-320.jpg)
![macro
(defmacro when [pred & body]
`(if ~pred (do ~@body) nil))
(when (> x 2)
(* x 4))
(if (> x 2)
(* x 4)
nil)](https://image.slidesharecdn.com/clojure-fromgroundup-150908064630-lva1-app6891/85/Clojure-from-ground-up-11-320.jpg)
![macro
(gen-from-tpl "exception {ex} at {line}")
(defmacro gen-from-tpl
[tpl-str]
(let [partitions (re-partition #"{((?:w|-)+)}" tpl-str)
string-and-symbol (map (fn [{:keys [match? result]}]
(if match?
(-> result second symbol)
result))
partitions)]
`(str ~@string-and-symbol)))
(str "exception" ex "at" line)](https://image.slidesharecdn.com/clojure-fromgroundup-150908064630-lva1-app6891/85/Clojure-from-ground-up-12-320.jpg)
![application
cascalog
(?- (stdout)
(<- [?word ?count]
(sentence :> ?line)
(tokenise :< ?line :> ?word)
(c/count :> ?count)))
SELECT word, COUNT(*)
FROM words
GROUP BY word](https://image.slidesharecdn.com/clojure-fromgroundup-150908064630-lva1-app6891/85/Clojure-from-ground-up-14-320.jpg)
![application
compojure
(defroutes user-routes
(POST “/login" [username password] users/login)
(GET "/user/:id" [id] users/get-by-id))
(context "/user/current" []
(GET "/" [] …)
(POST "/profile" [phone location] ...)
(GET "/posts" [text] ...)))](https://image.slidesharecdn.com/clojure-fromgroundup-150908064630-lva1-app6891/85/Clojure-from-ground-up-15-320.jpg)
Clojure from ground up
- 1. Clojure: from ground up R君
- 2. Agenda • Lisp & Clojure intro (GC, FP, immutable) • macro • application
- 3. Clojure Yet Another JVM Programming Language, a Lisp dialect.
- 4. (defn concat [xs ys]! (if (empty? xs)! ys! (let [[h & t] xs]! (cons h (concat t ys))))) Lots of Irritating Stupid Parentheses
- 5. (defn concat [xs ys]! (if (empty? xs)! ys! (let [[h & t] xs]! (cons h (concat t ys))))) LISt Processing
- 9. Functional Programming • function as first-class citizen • work by arguments and returning value (defn make-adder [base] (let [ref (atom base)] (fn [delta] (swap! ref (partial + delta)))))
- 10. Immutable m = new HashMap(); m.put(1, “a”); m.put(2, “b”); m = new PersistentHashMap(); m = m.assoc(1, “a”); m = m.assoc(2, “b”);
- 11. macro (defmacro when [pred & body] `(if ~pred (do ~@body) nil)) (when (> x 2) (* x 4)) (if (> x 2) (* x 4) nil)
- 12. macro (gen-from-tpl "exception {ex} at {line}") (defmacro gen-from-tpl [tpl-str] (let [partitions (re-partition #"{((?:w|-)+)}" tpl-str) string-and-symbol (map (fn [{:keys [match? result]}] (if match? (-> result second symbol) result)) partitions)] `(str ~@string-and-symbol))) (str "exception" ex "at" line)
- 13. application • strom • cascalog • compojure
- 14. application cascalog (?- (stdout) (<- [?word ?count] (sentence :> ?line) (tokenise :< ?line :> ?word) (c/count :> ?count))) SELECT word, COUNT(*) FROM words GROUP BY word
- 15. application compojure (defroutes user-routes (POST “/login" [username password] users/login) (GET "/user/:id" [id] users/get-by-id)) (context "/user/current" [] (GET "/" [] …) (POST "/profile" [phone location] ...) (GET "/posts" [text] ...)))
- 16. Why Clojure Java interop java.lang.Math/PI => 3.141592653589793 (.exists (java.io.File. "t1.clj")) => true (.toUpperCase "foo") => "FOO"
- 17. Q & A
- 18. Thanks