Programação FuncionalFISL 2013

Juarez Bochi

λSunday, July 14, 13

Juarez Bochi

Sunday, July 14, 13

Juarez Bochi

Sunday, July 14, 13

Juarez Bochi

Sunday, July 14, 13

Juarez Bochi

Sunday, July 14, 13

Juarez Bochi

Sunday, July 14, 13

Agenda

• Motivação

• Conceitos

• Exemplos

• Resumo

Sunday, July 14, 13

Motivação

Sunday, July 14, 13

Ler um arquivo, listar as palavras mais

comuns em ordem decrescente.

Sunday, July 14, 13

Ler um arquivo, listar as palavras mais

comuns em ordem decrescente.

Sunday, July 14, 13

Donald Knuth

X

Sunday, July 14, 13

Donald Knuth Doug McIlroy

X

Sunday, July 14, 13

Donald Knuth Doug McIlroy

X

10+ páginas de Pascal/WEBSunday, July 14, 13

Donald Knuth Doug McIlroy

X

10+ páginas de Pascal/WEB 6 linhas de shellSunday, July 14, 13

tr -cs A-Za-z '\n' |tr A-Z a-z |sort |uniq -c |sort -rn |sed ${1}q

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Sunday, July 14, 13

$ cat discurso.txt | tr -cs A-Za-z '\n' | tr A-Z a-z | sort | uniq -c | sort -rn | sed 40q 65 e 48 de 42 a 35 o 32 que 18 os 15 para 15 com 14 mais 13 nao 13 do 11 as 10 um 10 dos 10 da 9 das 8 ela 7 todos 7 se 7 pais 7 muito 6 ruas 6 brasil 5 violencia

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“Keep it simple, make it general, and make it intelligible.” Doug McIlroy

Sunday, July 14, 13

“Keep it simple, make it general, and make it intelligible.” Doug McIlroy

Sunday, July 14, 13

Conceitos

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Paradigmas

• Imperativo

• Lógico

• Funcional

• Orientado a Objetos

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Paradigma Imperativo

Linguagem Computador

Variáveis Mutáveis Endereço de memória

Estruturas de controle (if-then-else, loop)

Jumps

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“Can Programming Be Liberated from the von. Neumann Style?”John Backus - Turing Award Lecture

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Programação Funcional

• Concentrar em teorias, não mutações

• Minimizar mudança de estados

• Sem estruturas de controle imperativas

• Foco em funções

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“Programação Funcional é ortogonal à Orientação

a Objetos”

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Elementos de Programação

• Expressões Primitivas

• Meios de Combinação

• Meios de Abstração

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Exemplos

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First Class Functions

Sunday, July 14, 13

First Class Functions

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Closure> var inc, dec;undefined> function contador() {... var x = 0;... inc = function() { return ++x; };... dec = function() { return --x; };... }undefined> contador();undefined

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Closure> inc();1> inc();2> dec();1> dec();0> inc();1> xReferenceError: x is not defined

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> import Control.Applicative> let foo = fmap (+3) (+2)> foo 1015

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> import Control.Applicative> let foo = fmap (+3) (+2)> foo 1015

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> (defn soma3 [x] (+ x 3))

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> (defn soma3 [x] (+ x 3))

> (map soma3 [2 4 6])(5 7 9)

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> (defn soma3 [x] (+ x 3))

> (map soma3 [2 4 6])(5 7 9)

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> (defn soma3 [x] (+ x 3))

> (map soma3 [2 4 6])(5 7 9)

> (pmap soma3 [2 4 6])(5 7 9)

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Higher Order Functionpessoas = [{'nome': 'Adolfo', 'estado': 'MG'}, {'nome': 'Pedro', 'estado': 'RS'}, {'nome': 'Maria', 'estado': 'AC'}]

def por_estado(pessoa1, pessoa2): return cmp(pessoa1['estado'], pessoa2['estado'])

>>> pprint.pprint(sorted(pessoas, cmp=por_estado))[{'estado': 'AC', 'nome': 'Maria'}, {'estado': 'MG', 'nome': 'Adolfo'}, {'estado': 'RS', 'nome': 'Pedro'}]

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Recursão

Sunday, July 14, 13

Recursão

(define (fib n) .. (if (< n 2) .. n .. (+ (fib (- n 1)) (fib (- n 2))))) (fib 10)=> 55

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Tail Call Optimization1. fib(5)2. fib(4) + fib(3)3. (fib(3) + fib(2)) + (fib(2) + fib(1))4. ((fib(2) + fib(1)) + (fib(1) + fib(0))) + ((fibb(1) + fib(0)) + fib(1))5. (((fib(1) + fib(0)) + fib(1)) + (fib(1) + fib(0))) + ((fib(1) + fib(0)) +

fib(1))

Sunday, July 14, 13

Tail Call Optimization

(define (fib n) .. (letrec ((fib-aux (lambda (n a b) .. (if (= n 0) .. a .. (fib-aux (- n 1) b (+ a b)))))) .. (fib-aux n 0 1))) (fib 1000)=> 4.346655768693743e+208

1. fib(5)2. fib(4) + fib(3)3. (fib(3) + fib(2)) + (fib(2) + fib(1))4. ((fib(2) + fib(1)) + (fib(1) + fib(0))) + ((fibb(1) + fib(0)) + fib(1))5. (((fib(1) + fib(0)) + fib(1)) + (fib(1) + fib(0))) + ((fib(1) + fib(0)) +

fib(1))

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Sunday, July 14, 13

Currying & Partialsdef to_tag(tag, texto): return "<{tag}>{texto}</{tag}>".format(tag=tag, texto=texto)

Sunday, July 14, 13

Currying & Partials

def partial(funcao, argumento): def fn(arg): return funcao(argumento, arg) return fn

def to_tag(tag, texto): return "<{tag}>{texto}</{tag}>".format(tag=tag, texto=texto)

Sunday, July 14, 13

Currying & Partials

def partial(funcao, argumento): def fn(arg): return funcao(argumento, arg) return fn

def to_tag(tag, texto): return "<{tag}>{texto}</{tag}>".format(tag=tag, texto=texto)

negrito = partial(to_tag, 'b')italico = partial(to_tag, 'i')

Sunday, July 14, 13

Currying & Partials

def partial(funcao, argumento): def fn(arg): return funcao(argumento, arg) return fn

def to_tag(tag, texto): return "<{tag}>{texto}</{tag}>".format(tag=tag, texto=texto)

negrito = partial(to_tag, 'b')italico = partial(to_tag, 'i')>>> negrito(italico("Oi, FISL!"))"<b><i>Oi FISL!</i></b>"

Sunday, July 14, 13

Currying & Partials

def partial(funcao, argumento): def fn(arg): return funcao(argumento, arg) return fn

def to_tag(tag, texto): return "<{tag}>{texto}</{tag}>".format(tag=tag, texto=texto)

DSL!!negrito = partial(to_tag, 'b')italico = partial(to_tag, 'i')>>> negrito(italico("Oi, FISL!"))"<b><i>Oi FISL!</i></b>"

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Laziness

Sunday, July 14, 13

Laziness

Sunday, July 14, 13

Lazinessdef from(n: Int): Stream[Int] = n #:: from(n+1)

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Lazinessdef from(n: Int): Stream[Int] = n #:: from(n+1) 

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Lazinessdef from(n: Int): Stream[Int] = n #:: from(n+1) val nats = from(0)

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Lazinessdef from(n: Int): Stream[Int] = n #:: from(n+1) val nats = from(0) 

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Lazinessdef from(n: Int): Stream[Int] = n #:: from(n+1) val nats = from(0) def sieve(s: Stream[Int]): Stream[Int] =

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Lazinessdef from(n: Int): Stream[Int] = n #:: from(n+1) val nats = from(0) def sieve(s: Stream[Int]): Stream[Int] = s.head #:: sieve(s.tail filter (_ % s.head != 0))

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Lazinessdef from(n: Int): Stream[Int] = n #:: from(n+1) val nats = from(0) def sieve(s: Stream[Int]): Stream[Int] = s.head #:: sieve(s.tail filter (_ % s.head != 0)) 

Sunday, July 14, 13

Lazinessdef from(n: Int): Stream[Int] = n #:: from(n+1) val nats = from(0) def sieve(s: Stream[Int]): Stream[Int] = s.head #:: sieve(s.tail filter (_ % s.head != 0)) val primes = sieve(from(2))

Sunday, July 14, 13

Lazinessdef from(n: Int): Stream[Int] = n #:: from(n+1) val nats = from(0) def sieve(s: Stream[Int]): Stream[Int] = s.head #:: sieve(s.tail filter (_ % s.head != 0)) val primes = sieve(from(2)) 

Sunday, July 14, 13

Lazinessdef from(n: Int): Stream[Int] = n #:: from(n+1) val nats = from(0) def sieve(s: Stream[Int]): Stream[Int] = s.head #:: sieve(s.tail filter (_ % s.head != 0)) val primes = sieve(from(2)) (primes take N).toList

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Data Abstractionclass Zero(Natural): def __init__(self): pass

def __repr__(self): return "0"

def __add__(self, other): return other

Sunday, July 14, 13

Data Abstractionclass Zero(Natural): def __init__(self): pass

def __repr__(self): return "0"

def __add__(self, other): return other

class Natural(object): def __init__(self, anterior): self.anterior = anterior

def __repr__(self): return repr(self.anterior) + " + 1"

def __add__(self, other): return self.anterior + other.sucessor()

def sucessor(self): return Natural(anterior=self)

Sunday, July 14, 13

Data Abstractionclass Zero(Natural): def __init__(self): pass

def __repr__(self): return "0"

def __add__(self, other): return other

class Natural(object): def __init__(self, anterior): self.anterior = anterior

def __repr__(self): return repr(self.anterior) + " + 1"

def __add__(self, other): return self.anterior + other.sucessor()

def sucessor(self): return Natural(anterior=self)>>> zero = Zero()

>>> um = zero.sucessor()>>> dois = um.sucessor()>>> um0 + 1>>> dois0 + 1 + 1>>> um + dois0 + 1 + 1 + 1

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Resumo

Sunday, July 14, 13

Blub Paradox

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Resumo

Código fácil de entender

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Resumo

Código fácil de manter

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Resumo

Código fácil de testar

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Resumo

Código fácil de escalar

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Obrigado!@jbochi

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Referências• http://www.leancrew.com/all-this/2011/12/more-shell-less-egg/

• http://onesixtythree.com/literate/literate2.pdf

• http://mitpress.mit.edu/sicp/

• http://www.paulgraham.com/avg.html

• https://www.coursera.org/course/progfun

• http://www.slideshare.net/jbochi/programao-funcional-em-python

• https://raw.github.com/richhickey/slides/master/simplicitymatters.pdf

• http://pragprog.com/magazines/2013-01/functional-programming-basics

• http://adit.io/posts/2013-04-17-functors,_applicatives,_and_monads_in_pictures.html

• http://en.literateprograms.org/Fibonacci_numbers_(Scheme)

• http://norvig.com/21-days.html

• http://www.youtube.com/watch?v=3jg1AheF4n0

• http://www.flickr.com/photos/niceric/74977685/sizes/l/in/

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