Functional Geekery for an Imperative Mind

Slides for the talk at RubyConf India 2015

Transcript

1. FUNCTIONAL GEEKERY FOR AN IMPERATIVE MIND Rajeev N B
2. @rshetty on Github @rbharshetty on Twitter
4. SIMON PEYTON JONES
5. NIRVANA C, C++, Java, Ruby .. Haskell Nirvana Useful Less Useful Unsafe Safe
6. IMPERATIVE VS FUNCTIONAL
7. PROPERTY IMPERATIVE FUNCTIONAL FOCUS Changing existing values Declaring new values CONTROL FLOW Loops, Conditionals and Function calls Functional calls including Recursion MANIPULATION UNIT Instances of classes and structs Functions and Data Structures. MENTAL MODEL Algorithmic Programming Composing problems with set of functions.
8. FUNCTIONAL PROGRAMMING?
9. – John Hughes (Why Functional Programming Matters) “Functional Programming is so called because a program consists entirely of functions”
10. CONCEPTS
11. FUNCTION COMPOSITION (F O G)
12. It is the act of pipelining result of a function into input of another, creating a new function
13. Function g(x) x + 1 Function f(x) x * x x = 3 g(x)= 4 f(g(x))= 16
16. It is the act of pipelining result of a function into input of with another, creating a new function
20. LAZY EVALUATION
21. Evaluation of a expression is deferred until the result is needed by other computations
22. LAZY EVALUATION Call by need Infinite Data structures Thunks Performant
23. HIGHER ORDER FUNCTIONS
24. Functions which either take functions as arguments or return functions as return values
27. CURRYING
28. Transforming function that takes multiple arguments into function that takes single argument
31. PURE FUNCTION
32. Function that returns exactly the same result every time it is called with same set of arguments
33. Pure Function f(x) = Math.cos(x) Pure Function ( No Side Effects ) x f(x)
35. REFERENTIAL TRANSPARENCY Expression is referentially transparent if it can be replaced with its value Property of Pure functions No side effects Easier to reason about programs
36. WHY PURE FUNCTIONS? Reproducible results Memoization Parallelization
37. IMMUTABILITY
38. Immutable object is an object whose state cannot be modified after it is created
39. IMMUTABLE DATA STRUCTURES Data structure once created cannot be modified Uses sophisticated structure sharing
40. WHY? Concurrency Security
41. FUNCTIONAL THINKING
42. REFERENCES Haskell Wiki Learn You a Haskell Ruby Function Composition Resurgence of Functional Programming Code samples
43. THANKS
44. QUESTIONS?