Clojure and Modularity
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This document discusses Clojure's support for modularity through its data structures like lists, vectors, maps, and sets. It also covers Clojure's approach to namespaces, multimethods, vars, refs, agents, and dependency management compared to other languages and frameworks like CPAN, Rubygems, Maven, and OSGi.
![Clojure's Four Elements
List (print :hello "Philly")
Vector [:eat "Pie" 3.14159]
Map {:lisp 1 "The Rest" 0}
Set #{2 1 3 5 "Eureka"}](https://image.slidesharecdn.com/clojureslidesphilly2009-07-21-100131101136-phpapp01/85/Clojure-and-Modularity-3-320.jpg)
![defn
(defn greet [name]
(println "Hello," name))
(defn average [& args]
(/ (reduce + args) (count args)))](https://image.slidesharecdn.com/clojureslidesphilly2009-07-21-100131101136-phpapp01/85/Clojure-and-Modularity-4-320.jpg)
![Data are Functions
({:f "foo" :b "bar"} :f)
"foo"
(:key {:key "value", :x "y"})
"value"
([:a :b :c] 2)
:c
(#{1 5 3} 3)
true](https://image.slidesharecdn.com/clojureslidesphilly2009-07-21-100131101136-phpapp01/85/Clojure-and-Modularity-5-320.jpg)
![defmacro
(defmacro when [test & body]
(list 'if test (cons 'do body)))](https://image.slidesharecdn.com/clojureslidesphilly2009-07-21-100131101136-phpapp01/85/Clojure-and-Modularity-6-320.jpg)
![Vars
(def life 42)
(defn meaning [] (println life))
(meaning)
42
(binding [life 37] (let [life 37]
(println life)
(meaning)) (meaning))
37 37
42](https://image.slidesharecdn.com/clojureslidesphilly2009-07-21-100131101136-phpapp01/85/Clojure-and-Modularity-9-320.jpg)
![Agents
(def fib (agent [1 1 2]))
(deref fib)
[1 1 2]
(send fib conj 3 5) returns immediately!
later on...
(deref fib)
[1 1 2 3 5]](https://image.slidesharecdn.com/clojureslidesphilly2009-07-21-100131101136-phpapp01/85/Clojure-and-Modularity-11-320.jpg)
![clojure.contrib.http.agent
(http-agent
"http://www.altlaw.org/"
:on-success
(fn [a]
(println
(response-body-str a))))](https://image.slidesharecdn.com/clojureslidesphilly2009-07-21-100131101136-phpapp01/85/Clojure-and-Modularity-12-320.jpg)
![Multimethods
(defmulti copy
(fn [in out]
[(class in) (class out)]))](https://image.slidesharecdn.com/clojureslidesphilly2009-07-21-100131101136-phpapp01/85/Clojure-and-Modularity-13-320.jpg)
![Multimethods
(defmethod copy [InputStream OutputStream] ..
(defmethod copy [InputStream Writer] ...
(defmethod copy [InputStream File] ...
(defmethod copy [Reader OutputStream] ...
(defmethod copy [Reader Writer] ...
(defmethod copy [Reader File] ...
(defmethod copy [File OutputStream] ...
(defmethod copy [File Writer] ...
(defmethod copy [File File] ...](https://image.slidesharecdn.com/clojureslidesphilly2009-07-21-100131101136-phpapp01/85/Clojure-and-Modularity-14-320.jpg)
![Namespaces
(ns my.cool.project
(:require [clojure.contrib.math :as math])
(:import (java.math BigDecimal)))
(defn lower-median [x y]
(math/floor (/ x y))](https://image.slidesharecdn.com/clojureslidesphilly2009-07-21-100131101136-phpapp01/85/Clojure-and-Modularity-15-320.jpg)
Clojure and Modularity
- 1. Clojure and Modularity Philly Lambda Tuesday, July 21, 2009 Stuart Sierra http://stuartsierra.com/
- 3. Clojure's Four Elements List (print :hello "Philly") Vector [:eat "Pie" 3.14159] Map {:lisp 1 "The Rest" 0} Set #{2 1 3 5 "Eureka"}
- 4. defn (defn greet [name] (println "Hello," name)) (defn average [& args] (/ (reduce + args) (count args)))
- 5. Data are Functions ({:f "foo" :b "bar"} :f) "foo" (:key {:key "value", :x "y"}) "value" ([:a :b :c] 2) :c (#{1 5 3} 3) true
- 6. defmacro (defmacro when [test & body] (list 'if test (cons 'do body)))
- 7. Java (import '(com.example.package MyClass YourClass)) (.method object argument) (MyClass/staticMethod argument) (MyClass. argument)
- 8. synchronous asynchronous coordinated ref independent atom agent unshared var
- 9. Vars (def life 42) (defn meaning [] (println life)) (meaning) 42 (binding [life 37] (let [life 37] (println life) (meaning)) (meaning)) 37 37 42
- 10. Refs (def c (ref 100)) (deref c) 100 (dosync (alter c inc)) (deref c) 101
- 11. Agents (def fib (agent [1 1 2])) (deref fib) [1 1 2] (send fib conj 3 5) returns immediately! later on... (deref fib) [1 1 2 3 5]
- 12. clojure.contrib.http.agent (http-agent "http://www.altlaw.org/" :on-success (fn [a] (println (response-body-str a))))
- 13. Multimethods (defmulti copy (fn [in out] [(class in) (class out)]))
- 14. Multimethods (defmethod copy [InputStream OutputStream] .. (defmethod copy [InputStream Writer] ... (defmethod copy [InputStream File] ... (defmethod copy [Reader OutputStream] ... (defmethod copy [Reader Writer] ... (defmethod copy [Reader File] ... (defmethod copy [File OutputStream] ... (defmethod copy [File Writer] ... (defmethod copy [File File] ...
- 15. Namespaces (ns my.cool.project (:require [clojure.contrib.math :as math]) (:import (java.math BigDecimal))) (defn lower-median [x y] (math/floor (/ x y))
- 16. Modularity and Dependency Management ● CPAN ● OSGi ● Python Eggs ● Maven ● Rubygems ● Ivy ● PEAR (PHP)
- 17. Modularity Your program Library X Library Y Library Z, Library Z, version 1 version 2
- 18. "JAR hell" Your program x.jar y.jar Library X Library Y Library Z, Library Z, version 1 version 2
- 19. CPAN ● System-wide or per-user library installation ● User manages libraries ● One repository, many mirrors ● Multiple versions of a lib may be installed; each process may only use one version ● Integrated docs, tests, & bug tracker
- 20. Rubygems ● System-wide or per-user library installation ● User manages libraries ● Multiple repositories, names may conflict ● Multiple versions of a lib may be installed; each process may only use one version ● Docs, tests, and bug tracking not integrated
- 21. ASDF ● System-wide or per-user library installation ● User manages libraries ● Wiki page acts as the repository! ● No integrated docs/tests/bug-tracking ● Does not support multiple versions of the same lib
- 22. Maven / Ivy ● Per-project library installation ● Build system manages libraries; user manages private repository ● Multiple public repositories ● Optional integration with docs/tests ● Permits multiple versions of a same lib, must be handled by a framework
- 23. OSGi ● Java EE, Glassfish, Eclipse ● Bundle: JAR file + extra manifest headers ● Each Bundle gets its own ClassLoader ● Multiple, nested ClassLoader contexts within a single JVM
- 24. More ● http://clojure.org/ ● Google Groups: Clojure ● #clojure on irc.freenode.net ● http://github.com/richhickey/clojure-contrib ● http://stuartsierra.com/ ● http://github.com/stuartsierra ● http://www.altlaw.org/