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![Persistent Data Structures - List, Vector, Map & Set Clojure’s built-in data structures are all immutable - returning a new data structure when a function is applied (list 1 2 3 4 5) ‘(“fish” “chips” 42) (vec ‘(1 2 3 4)) [1 2 3 4] {:key “value”} {:name “John” :skill “conferencing”} (set ‘(1 2 3 4 4)) #{1 2 3 4}](https://image.slidesharecdn.com/functionalwebwithclojure-160322211047/75/Functional-web-with-clojure-14-2048.jpg)
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Functional web with clojure
This document discusses functional programming with Clojure. It explains why functional programming aims to eliminate side effects by making functions pure. Clojure allows for functional programming through features like immutable persistent data structures, higher order functions, recursion with tail call optimization, and lazy evaluation. Concurrency in Clojure is easier due to immutability, persistent data structures, and software transactional memory. The document provides examples of building web applications in Clojure using Ring, Compojure, and Hiccup. It also discusses building client-side apps with ClojureScript. Resources for learning Clojure like books, websites, and communities are mentioned.
Functional web with clojure
- 1. Functional Web withClojure by John Stevenson @jr0cket clojure.practical.li
- 2. @jr0cket Speaker, author, conferenceorganiser & community obsessed developer. Love Clojure, Emacs, Cats, Cycling & Agile development. @Heroku @SalesforceDevs #Trailhead In a galaxy far, far away… London, UK
- 3. Why Functional Programming it'snot just because it's really fun...
- 4. OO Software in action Josh Smith- Tweet Original Gif
- 5. The Complexity Iceberg -@krisajenkins ● complexity is very dangerous when hidden ● You can't know what a function does for certain if it has side effects
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- 7. Pure Functions The resultsof the function are purely determined by its initial output and its own code - no external influence, a function only uses local values - referential transparency (the function can be replaced by its value)
- 8. Impure Functions -side causes The results of the function are purely determined by its initial output and its own code - behaviour externally influenced and non-deterministic
- 9. Eliminating Side Effects Functionalprogramming is about eliminating side effects where you can, controlling them where you can't - @krisajenkins The features in Functional Programming come from a desire to reduce side effects
- 10. Clojure General purpose languagehosted on JVM, JavaScript & CLR
- 11. Clojure / ClojureScript Ahosted language with simple interoperability with the host language - (java.Util.Date.) - (js/alert “Client side apps are easier in Clojure”)
- 12. Clojure - basicsyntax for this talk ( ) ;; an empty list. The first element of a list is evaluated as a function call (function-name data) ;; call a function with the data as its argument (def name “data-or-value”) ;; assign (bind) a name to a data or legal value :keyword-name ;; a keyword is a name that points to itself ;; Thread-first macro - chain function calls, passing the result of each call as the first argument to the next function. The ,,, indicates where the resulting argument goes. (-> (function-a “data”) (function-b ,,,) ;; In Clojure commas , are whitespace (function-c ,,, “data”))
- 13. Removing boilerplate codeby not defining types ever where
- 14. Persistent Data Structures -List, Vector, Map & Set Clojure’s built-in data structures are all immutable - returning a new data structure when a function is applied (list 1 2 3 4 5) ‘(“fish” “chips” 42) (vec ‘(1 2 3 4)) [1 2 3 4] {:key “value”} {:name “John” :skill “conferencing”} (set ‘(1 2 3 4 4)) #{1 2 3 4}
- 15. Persistent Data Structuresshared memory Each function creates a new vector Memory space for values is shared between each vector
- 16. Persistent Data Structures sharedmemory By sharing memory you can apply functions over and over again effectively Values persist until they are no longer referenced
- 17. Higher Order Functions Functionsalways return a value & can be used as an argument to another function
- 18. Composing functions together Example:current value of the Clojure project from the configuration file - `slurp` in the project file, convert into a string and return the value at index 2
- 19. Recursion Process a collectionof values by feeding the remaining elements back to the function - the sum function is polymorphic, it has different behaviours that could be evaluated depending on if passed 1 or 2 arguments
- 20. Recursion - tailcall optomisation Protect the heap space from blowing by using the recur function Using recur in the last line is the same as calling sum, however the memory required from the previous sum function call is over-written in memory. So only 1 memory slot is used instead of 10 billion
- 21. Lazy Evaluation Only returna value when necessary ● maintain precision ● optomise evaluation
- 22. Sequence / ListComprehension Iterate over collections
- 23. Sequence / ListComprehension Iterating through a range of generated values to create a list of 2 value vectors
- 24. Immutability - localbinding Assignments made locally are immutable
- 25. Concurrency is Easier Concurrencyis much easier to write and reason about because of - Immutability by default - Persistent Data Structures - values are immutable - functional isolation & pure functions - state changes managed atomically (software transactional memory) - core.async library allows you to write asynchronous code as easily as sequential code
- 26. Safe State changes Changingstate safely by not changing it ● Persistent data structures ● Local bindings Changing state safely by changing it atomically ● Software Transactional Memory (STM) ○ Gives an mechanism like an in-memory atomic database that manages mutable state changes under the covers ● Atoms ● core.async
- 27. Concurrency syntax -atoms An online card game has players that can join and have their winnings tracked
- 28. Concurrency syntax -atoms The join-game function adds players to the atom by their name, but only up to 2 players
- 29. Concurrency syntax -refs for sync updates The join-game-safely adds players to the ref and alters their account & game account
- 30. Putting all thebasics together Let's find all the most common words used in a popular Science Fiction novel
- 31. Clojure - FunctionalWeb Immutability & composable functions for Web Apps
- 32. Ring - simplifyingcommunication Ring takes requests over HTTP and converts them into a map (think JSON)
- 33. Ring - creatingan embedded server
- 34. Compojure - simplifyingrouting Compojure routes requests based on path & request type
- 35. Compojure - definingroutes
- 36. Hiccup - htmlfrom Clojure
- 37. Ring - embeddedserver & dependencies
- 38. ClojureScript - FunctionalWeb Immutability & composable functions for Web Apps
- 41. jQuery over allJavaScript frameworks
- 43. Google Closure tools& libraries
- 45. ClojureScript Just add thedependencies & include the generated JavaScript
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- 49. Figwheel (flappy birdsexample)
- 50. Tools to learnClojure inspire them & build up their motivation
- 51. Clojure support inmany different tools
- 52. Leiningen - Clojurepowered build automation
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- 56. Figwheel (flappy birdsexample)
- 58. Examples, examples, examples welearn by example...
- 59. Over 20 Bookson Clojure... Where to start with Clojure will be different... Example: I typically suggested BraveClojure.com as a starting point, however many people prefer LivingClojure or ClojureScript Unraveled... Help people understand the relevance of a book and if it's the right thing for them at that time.
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- 66. Testing your Clojureskills...
- 68. Clojurian Community inPerson Probably the most active language-specific developer communities in London
- 69. Learning by teachingothers I really started thinking in Clojure when I started talking to & teaching others - Coding dojos - talks on Clojure (starting with the basics, showing the art of the possible) - moving on to running conferences - workshops at hack days
- 70. Overtone live performance- MetaX
- 71. Overtone live performance- MetaX
- 72. Take your ownjourney into Clojure
- 73. @jr0cket @Heroku @SalesforceDevs #Trailhead In a galaxyfar, far away… London, UK