Introduction to Functional Programming and Clojure
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This document provides an introduction to functional programming concepts and the Clojure programming language. It outlines what will be covered, including looking at programming without for-loops or mutable data, understanding functional programming basics in the context of Clojure, and why considering a functional style and Clojure may benefit projects. Key functional programming concepts like pure functions, recursion over iteration, and referential transparency are introduced. Clojure is described as a Lisp for the JVM that uses an immutable and functional style while interoperating with Java. The document gives examples of Clojure syntax including functions, lists, and map/filter/reduce operations before concluding with questions.
Introduction to Functional Programming and Clojure
- 1. Introduction to Functional Programming and Clojure @sdaas
- 2. What to Expect … • Look at programming in a different way – Immutable data – A world without for-loops • Understand basics of functional programming – In the context of Clojure • A POV on why to consider a functional programming style in your current project • And why Clojure might be a good choice
- 3. What NOT to Expect … • NOT a deep dive into all aspects of the Clojure programming language • NOT about installation, debugging, performance, etc. of Clojure • NO bashing of Java or any other language • NO bashing of Object-Oriented Design
- 4. Don’t forget Java yet … • FP is a programming paradigm or style • Some languages lend themselves better to functional programming – Clojure, Haskell, Erlang • Most languages support FP to some extent – Java 8 – JavaScript – Python
- 5. Functional Programming Concepts • More like Mathematical Functions – vs. Subroutines/procedures • Support higher order functions • Pure functions – with no side effects • Recursion is favored over iteration • Lazy Evaluation • Referential Transparency – Once defined, a “variable” never changes value
- 6. What is Clojure ? • Created by Rich Hickey • Immutable and Functional Programming style • Lisp that runs on the JVM • Interoperates with Java • Power of Functional Programming meets the Richness of Java Ecosystem
- 8. Functions
- 9. Lists • Collection of heterogeneous values • Operations on lists never modify the original list. They always return a copy. • This “immutability” of data structure is a big deal in Functional Programing. • Two fundamental operators – first, & rest • Every data structure and function is built up using these two operators
- 10. Lists
- 11. Building Blocks – first & rest • Favoring recursion over iteration • Do you see the bomb in the nth-element ?
- 12. Tail recursion is your friend
- 13. Map, Filter, and Reduce
- 14. Composition • FP encourages you to compose small/simpler function to create complex functions
- 15. What does this code do ?
- 16. Sum of square of all odd numbers .. • How testable and maintainable is this code ? • Modify this for odd numbers that aren’t multiples of 7 ? • How would this work for infinitely long data ?
- 18. Find the first 20 prime numbers
- 19. Laziness is good ... • Iterate : returns lazy sequence of f(x) f(f(x)) etc .. • take : returns a lazy sequence of first n from collection • Map and filter can work on lazy sequences • Check out the call to java.lang.Math.sqrt
- 20. Hash Maps
- 21. Reading a CSV File … FROM Smith,John,45,90210 Frank,Peter,25,90110 Bond,James,38,90110 TO {:zip 90210, :age 45, :fname "John", :lname "Smith"} {:zip 90110, :age 25, :fname "Peter", :lname "Frank"} {:zip 90110, :age 38, :fname "James", :lname "Bond"}
- 22. 12 lines of Clojure Code …
- 23. What the %$*&^ was that ?
- 24. In Summary … • FP concepts can be used to create concise, highly modular, and composable code • Java 8 and JavaScript have good support for FP concepts • Clojure interoperates well with Java, and could be a good way to experiment with FP without abandoning the Java ecosystem
- 25. Questions ? Please give your feedback at http://bit.ly/introfp
- 26. Resources • The SICP Book “Structure and Interpretation of Computer Programs” • Paul Graham’s Blogs • Clojure Home page (clojure.org) • Clojure for the Brave and True (braveclojure.com) • www.slideshare.net/SoumendraDaas/present ations • www.github.com/sdaas/clojure-talk • https://medium.com/@sdaas/functionally- speaking-f4dba2a1c7ee