Some basic FP concepts
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This document discusses functional programming concepts like pure functions, immutable data, and avoiding side effects. It notes that FP uses higher-order functions, function composition, and transformation of immutable data structures rather than mutable state and assignment. FP allows for easier reasoning about programs, safer concurrency, and avoids problems introduced by mutable state. The document also advocates for representing data simply without defining classes and encourages practicing FP to understand its benefits.
![Higher-Order Function
Fn: [Any... -> Any]
F: [Any -> Fn]
G: [Fn -> Any]
H: [Fn -> Fn]
A function that
- does something with another function
- or returns a function,
- or both.](https://image.slidesharecdn.com/basic-fp-concepts-140829154828-phpapp01/85/Some-basic-FP-concepts-18-320.jpg)
![Function Application
Fn: [Any... -> Any]
apply: [Fn Any* -> Any]
Take collection of param values
and invoke function.](https://image.slidesharecdn.com/basic-fp-concepts-140829154828-phpapp01/85/Some-basic-FP-concepts-19-320.jpg)
![Partial Application
Fn: [Any1...Anym...Anyn -> Any]
partial: [Fn Any1...Anym ->
[Anym+1...Anyn -> Any]]
Create a new function with some arguments
fixed.
(„Currying“ is automatic partial application.)](https://image.slidesharecdn.com/basic-fp-concepts-140829154828-phpapp01/85/Some-basic-FP-concepts-20-320.jpg)
![Function Composition
F: [X -> Y]
G: [Y -> Z]
compose: [G F -> [X -> Z]]
Concatenate computations.](https://image.slidesharecdn.com/basic-fp-concepts-140829154828-phpapp01/85/Some-basic-FP-concepts-21-320.jpg)
Some basic FP concepts
- 1. Some basic FP concepts @friemens
- 2. Why is mutable state problematic? Functions as Values Programming without assignment? Handle mutable state safely Leave data alone!
- 3. Nothing new here! 1930s Lambda Calculus 1960s Lisp 1990s Haskell
- 4. „Familiarity and Simplicity are orthogonal concepts.“ Rich Hickey
- 5. Why is mutable state problematic?
- 6. A system without side-effects is useless, but...
- 8. Mutable state increases test effort.
- 9. 1. 2. Mutation introduces order.
- 10. Mutable state makes concurrency hard.
- 11. FP programming OOP programming Side-effects restrict how the machine can help us.
- 13. Context dependance Pure Functions Side-effects The future-proof structure of any software system.
- 15. Pure Function = No side-effects + Result depends only on param values
- 16. Lambda Expression = An anonymous function.
- 17. Closure = A function + some captured environment.
- 18. Higher-Order Function Fn: [Any... -> Any] F: [Any -> Fn] G: [Fn -> Any] H: [Fn -> Fn] A function that - does something with another function - or returns a function, - or both.
- 19. Function Application Fn: [Any... -> Any] apply: [Fn Any* -> Any] Take collection of param values and invoke function.
- 20. Partial Application Fn: [Any1...Anym...Anyn -> Any] partial: [Fn Any1...Anym -> [Anym+1...Anyn -> Any]] Create a new function with some arguments fixed. („Currying“ is automatic partial application.)
- 21. Function Composition F: [X -> Y] G: [Y -> Z] compose: [G F -> [X -> Z]] Concatenate computations.
- 23. Good bye =, for, while and cousins, ... … say hello to let, map, filter and friends!
- 24. map Thinking in collection transformations. xs ys z filter concat reduce
- 25. map filter mapcat into Don't be so eager!
- 26. Cheap parallelization. reduce combine
- 27. Handle mutable state safely
- 28. State x State x' f swap! Identity Separate state from identity.
- 29. Give identities well-defined concurrency semantics.
- 30. Share immutable state liberally. Be restrictive with access to identities.
- 32. BigHero -a string -a map +method1 +method2 +method3 Objects claim feature completeness.
- 33. You can't foresee the future.
- 34. You will violate the Open-Closed-Principle.
- 35. „Inventing a class with its own interface to hold a piece of information is like inventing a new language to write every short story. “ Rich Hickey
- 36. Data is simple.
- 37. DSL API Data Model
- 38. Wrap up
- 39. OO makes code understandable by encapsulating moving parts. FP makes code understandable by minimizing moving parts. Michael Feathers
- 40. The future is functional. You need to practice FP before you „get“ it. It's more fun!
- 41. Questions?