Functional programming ruby mty
- 1. Functional Programming Concepts and Ruby Adrian Francke (@adrian2112)
- 2. Why I started to learn functional programming 1. Interesting and useful concepts for general software development 2. For fun Structure and Interpretation of Computer Programs (SICP) http://en.wikipedia.org/wiki/ Structure_and_Interpretation_of_Computer_Programs
- 3. 1. Interesting and useful concepts for general software development 2. For fun Structure and Interpretation of Computer Programs (SICP) http://en.wikipedia.org/wiki/ Structure_and_Interpretation_of_Computer_Programs (3. Hipster) Why I started to learn functional programming
- 4. Goal of this talk 1. Show some functional programming concepts which can be used in your day to day programming in a non-functional programming language 2. Get you interested in functional programming
- 5. What is functional programming? Declarative vs Imperative Functional Programming is a kind of declarative programming Imperative “Describes computation in terms of statements that change a program state (...) describing how a program operates.” http://en.wikipedia.org/wiki/Imperative_programming Declarative “A style of building the structure and elements of computer programs, that expresses the logic of a computation without describing its control flow. (...) describing what the program should accomplish (...), rather than describing how” http://en.wikipedia.org/wiki/Declarative_programming
- 7. Examples Imperative Functional Imperative: http://www.siafoo.net/snippet/306 Functional: http://en.literateprograms.org/Quicksort_%28Haskell%29
- 8. Functional Programming concepts: Recursion ● Is a method where the solution to a problem depends on solutions to smaller instances of the same problem ● Recursion, see Recursion ● Recursion is heavily used in functional programming as it is the canonical and often the only way to iterate Image from: http://learnyouahaskell.com/
- 10. Functional Programming concepts: Higher order functions ● Functions that take other functions as their arguments ● Functions that returns other functions
- 11. Functional Programming concepts: Higher order functions ● Higher order function example ● accumulate from http://mitpress.mit.edu/sicp/full-text/book/ book-Z-H-15.html#%_sec_2.2.3
- 12. Functional Programming concepts: Purity ● Referential transparency ● Lazy evaluation
- 13. Functional Programming concepts: Referential transparency ● A program (or function) that has the same effects and output on the same input ● Allows the programmer and the compiler to reason about program behavior ● Try to make all functions referential transparent and keep the side effects in one place
- 14. Functional Programming concepts: Referential transparency Useful Useless Unsafe (side effects everywhere) Safe (Limited side effects) • C • Java • … “normal” languages • Haskell • (probably other pure funcional laguages) https://www.youtube.com/watch?v=iSmkqocn0oQ Future
- 15. Functional Programming concepts: Referential transparency ● A pure function can always be replaced by its result. ● There’s no difference between Math.cos(Math::PI) and -1.0 ● A function which calls an impure function is impure as well. Impurity is contagious http://www.sitepoint.com/functional-programming-pure- functions/
- 16. Functional Programming concepts: Referential transparency Example from: http://valve.github.io/blog/2014/07/04/from-object-to-functional-immutability/ Referential opaque Referential transparent
- 17. Functional Programming concepts: Referential transparency ● Easy to test (it does not depend on anything but its input) ● Easy maintenance ● Concurrency/parallelization
- 18. Functional Programming concepts: Referential transparency Example from: http://www.sitepoint.com/functional-programming-pure-functions Same function. Only if it is a pure function
- 19. Functional Programming concepts: Lazy evaluation ● Pure functions can be performed at any time and still yield the same result. ● Defer the computation of values until they are needed ● Example
- 20. Which of this concepts I use in ruby and how ● Higher order functions o map o reduce o select o find ● Pure functions (referential transparency)
- 21. Use attr_reader instead of attr_accessor so once defined it cannot be changed
- 22. Keep side effects in one place
- 23. Use of higher order functions
- 24. This functions depend on self.date. Should I send the date as parameter?
- 25. Current stand = Lets take this functions as “curried” or partially applied with the objects date. self.date not modifiable
- 26. Conclusions ● Learn new approaches to solve problems ● Try functional programing!! ● It will help you to create better code. A language that doesn’t affect the way you think about programming, is not worth knowing. — Alan Perlis
- 27. Resources ● Structure and Interpretation of Computer Programs (SICP) http:// mitpress.mit.edu/sicp/full-text/book/book-Z-H-38.html# %_index_start ● Programming with Nothing http://codon.com/programming-with- nothing
- 28. References ● Haskell wiki https://wiki.haskell.org/Functional_programming ● Composing programs (Higher order functions) http:// www.composingprograms.com/pages/16-higher-order- functions.html ● Learn You a Haskell for Great Good! http://learnyouahaskell.com ● http://www.sitepoint.com/functional-programming-pure-functions/