Impactos no design com o uso de programação funcional

1. Globalcode – Open4education
Impactos no design utilizando
programação funcional
Luiz Costa
gutomcosta@gmail.com / @gutomcosta

2. twitter.com/gutomcosta
github.com/gutomcosta
www.sagadoprogamador.com.br
medium.com/saga-do-programador

3. orientação a objetos

4. conjunto de ideias
encapsulamento polimorfismo
objetos herança
estado ...

5. programação funcional

6. conjunto de ideias
funções higher-order functions
imutabilidade lazy evaluation
recursão ...

7. Dois estilos de escrita

8. código imperativo
Foco no “como fazer”

9. código declarativo
Foco no “o que fazer”

10. código declarativo
Foco no “o que fazer”

11. “When writing a modular program to solve a problem,
one first divides the problem into subproblems, then
solves the subproblems, and finally combines the
solutions. The ways in which one can divide up the
original problem depend directly on the ways in which
one can glue solutions together.”
“Why functional programming matters”
-John Hughes in Research topics in functional programming, 1990

12. “When writing a modular program to solve a problem,
one first divides the problem into subproblems, then
solves the subproblems, and finally combines the
solutions. The ways in which one can divide up the
original problem depend directly on the ways in which
one can glue solutions together.”
“Why functional programming matters”
-John Hughes in Research topics in functional programming, 1990

13. “When writing a modular program to solve a problem,
one first divides the problem into subproblems, then
solves the subproblems, and finally combines the
solutions. The ways in which one can divide up the
original problem depend directly on the ways in which
one can glue solutions together.”
“Why functional programming matters”
-John Hughes in Research topics in functional programming, 1990

14. ..argue in the remainder of this paper that functional
languages provide two new, very important kinds of
glue.
“Why functional programming matters”
-John Hughes in Research topics in functional programming, 1990
higher order function lazy evaluation

15. building blocks

16. first class functions
uma variável?

17. invocando uma função
função como parâmetro

18. invoca a função

19. mesma função variando comportamento
dados e funções separados

20. higher order function
uma funcão que recebe outra função como
argumento ou retorna uma função

21. Como First Class
Functions e Higher
Order Functions podem
impactar nas decisões
de design?

22. OO foco na estrutura
Como substituir uma implementação em
runtime?

23. FP foco na transformação
transformação?

24. listas, map, reduce, filter

25. map
capitalize capitalize capitalize
Jose Paulo Luiz
jose luizpaulo
TextTextTextText
clojure.string

26. focus on results, not
steps
“Functional Thinking”
-Neal Ford - IBM Developer Works series

27. Filter clojure.string
1 2 3 4 5 6 7 8 9

28. Argentum
Análise de Candlesticks, bolsa de valores

29. Candlesticks

30. Argentum
Domain Model

31. como representar os
conceitos?
Negócio, Candlestick

33. define uma abstração

34. dados e funções separados

35. decompose an algorithm into functions that are
simple, meaningful and useful.
“Tutorial on Good Lisp Programming Style”
-Peter Norvig in 1992

36. decompose an algorithm into functions that are
simple, meaningful and useful.
“Tutorial on Good Lisp Programming Style”
-Peter Norvig in 1992

37. decomposição
invariantes

38. decomposição
dependência de outro
namespace

39. Argentum
Geração de gráfico com indicadores define uma
abstração
define comportamentos diferentes

40. como variar o
comportamento?

41. declara as funções

42. compondo funções
higher order functions
decomposição de função

43. calculando a média móvel

44. com diferentes
building blocks, é
preciso repensar as
decisões de design

45. OO e FP Juntos?

46. Functional in the small, OO in the large.
“Tell Above, and Ask Below - Hybridizing OO and Functional design”
-Michael Feathers, blog post

47. Functional Core, imperative shell.
“Destroy all software - episode 72”
-Gary Bernhardt, destroy on software screen cast series

48. conclusão

49. Functional Programming is more
a mindset than a particular set
of tools or languages.
“Functional Thinking”
-Neal Ford - IBM Developer Works series

50. Obrigado

51. Referências
SICP - http://mitpress.mit.edu/sicp/full-text/book/book.html
Why functional programming matters - http://www.cs.kent.ac.uk/people/staff/dat/miranda/whyfp90.pdf
Clojure - http://clojure.org/
Functional Thinking - http://www.ibm.com/developerworks/java/library/j-ft1/index.html
Tell Above, and ask Below - http://michaelfeathers.typepad.com/michael_feathers_blog/2012/03/
tell-above-and-ask-below-hybridizing-oo-and-functional-design.html
Functional Core, imperative shell - https://www.destroyallsoftware.com/screencasts/catalog/
functional-core-imperative-shell
Tutorial on good lisp programming style - http://www.cs.umd.edu/~nau/cmsc421/norvig-lisp-
style.pdf