Clojure - Why does it matter?
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Clojure is a Lisp dialect that runs on the JVM. It focuses on simplicity through immutable data, pure functions, and avoidance of side effects. Clojure allows for advanced techniques through its powerful core library, support for functional programming concepts like laziness, and libraries for concurrency and logic programming. The language is designed to enable deconstruction of applications into small, independent parts through its focus on separation of concerns and emphasis on code as data.
![Functional programming
Functions as values
Powerful data structures
„[...] a unit tester's wet dream.“
No assignments
Laziness](https://image.slidesharecdn.com/clojure-whydoesitmatter-140327013631-phpapp01/85/Clojure-Why-does-it-matter-14-320.jpg)
![Concise code
public <K,V> Map<V, K> revertKeysVals(Map<K, V> src) {
final Map<V, K> dst = new HashMap<V, K>();
for (Map.Entry<K, V> e : src.entrySet()) {
dst.put(e.getValue(), e.getKey());
}
return dst;
}
(defn revert-kv [m]
(->> m (map (juxt second first)) (into {})))](https://image.slidesharecdn.com/clojure-whydoesitmatter-140327013631-phpapp01/85/Clojure-Why-does-it-matter-16-320.jpg)
Clojure - Why does it matter?
- 1. Clojure Why does it matter? @friemens
- 2. ● Published 2008 by Rich Hickey. ● Dynamically typed. ● Compiles to bytecode. A pragmatic Lisp for the JVM
- 5. Few ubiquitous data structures and powerful core library. Simple Complicated Data encapsulated behind specific APIs of OO classes. Immutable data. Mutable class instances & synchronization. Embedded „code generators“. External DSL tooling. Pure functions. Side effects & dependence on context.
- 6. Design is deconstruction Small libraries, no big frameworks! HTTP server Middle- ware functions Routing function Handler functions Page renderer
- 7. Deconstructing the database Datomic A modular, facts-based database system. Storage service Transactor Query Cache Peer library Application Database
- 8. State and Identity OO style (conflated) Clojure style (separated)
- 12. The elegance of Lisp
- 14. Functional programming Functions as values Powerful data structures „[...] a unit tester's wet dream.“ No assignments Laziness
- 15. Example: Square root approximation gn+1 := (n/gn + gn) / 2
- 16. Concise code public <K,V> Map<V, K> revertKeysVals(Map<K, V> src) { final Map<V, K> dst = new HashMap<V, K>(); for (Map.Entry<K, V> e : src.entrySet()) { dst.put(e.getValue(), e.getKey()); } return dst; } (defn revert-kv [m] (->> m (map (juxt second first)) (into {})))
- 17. Prefer purity Pure functions Side effects Context
- 18. Code is data, or: why does Lisp look different? Code Data
- 19. Common How it could be Build config DSL grammar Settings Serialization XML Xtext .properties JSON Debug output Anything EDN EDN EDN EDN EDN Clojure is a superset of Extensible Data Notation
- 20. A powerful language allows for simpler tools
- 24. Persistent datastructures 0 1 2 3 4 5 6 6 7 8 9 10 7
- 25. Concurrency support Actor style: Pulsar librarySoftware Transactional Memory CSP style: core.async library Widely used: Synchronization and LockingJava Clojure
- 26. Advanced libraries core.logic core.async core.typed core.reducers Datomic map + fold parallelized Logic programming CSP style programming Optional type system Facts-based database
- 27. Internal DSLs just happen HTTP routing UI form description Data access
- 28. Full stack Clojure Browser App Server Database ClojureScript Clojure Datomic
- 30. Advanced thinking Expressive power Fosters dev skills Advanced concurrency support Perfect for unit testing What's in for you? Concise data manipulation Interactive programming
- 31. Thank you. Questions? @friemens www.itemis.de