Add translate until list comprehensions

I'm translating haskell guide from Adit Bhargava (learnxinyminutes contribuitor) but adding a few more stuff about haskell

pt-br/haskell-pt.html.markdown

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+---
+linguagem: haskell
+tradutor/contribuidor:
+    - ["Lucas Tonussi", "http://www.inf.ufsc.br/~tonussi/"]
+---
+
+As linguagens funcionais são linguagens de programação com base em avaliação
+de funções matemáticas (expressões), evitando-se o conceito de mudança de
+estado com alteração de dados. Neste aspecto, este paradigma é oposto ao
+paradigma imperativo que se baseia em alterações de estados.
+
+A programação funcional começou no cálculo lambda, que foi base teórica para
+o desenvolvimento deste paradigma de programação.
+
+
+```haskell
+-- Para comentar a linha basta dois traços seguidos.
+
+{- Abre chaves traço e traço fecha chaves cria um campo
+   para comentário em múltiplas linhas.
+-}
+
+----------------------------------------------------
+-- 1. Tipos Primitivos de Dados e Operadores
+----------------------------------------------------
+
+-- Numerais
+
+0 -- 3
+1 -- 1
+2 -- 2 ...
+
+-- Alguns Operadores Fundamentais
+
+7 + 7 -- 7 mais 7
+7 - 7 -- 7 menos 7
+7 * 7 -- 7 vezes 7
+7 / 7 -- 7 dividido por 7
+
+-- Divisões não são inteiras, são fracionádas por padrão da linguagem
+28736 / 82374 -- 0.3488479374559934
+
+
+-- Divisão inteira
+82374 `div` 28736 -- 2
+
+-- Divisão modular
+82374 `mod` 28736 -- 24902
+
+-- Booleanos como tipo primitivo de dado
+True -- Verdadeiro
+False -- Falso
+
+-- Operadores unitário
+not True -- Nega uma verdade
+not False -- Nega uma falácia
+
+
+-- Operadores binários
+7 == 7 -- 7 é igual a 7 ?
+7 /= 7 -- 7 é diferente de 7 ?
+7 < 7 -- 7 é menor que 7 ?
+7 > 7 -- 7 é maior que 7 ?
+
+
+{- Haskell é uma linguagem que tem uma sintáxe bastante familiar na
+   matemática, por exemplo em chamadas de funções você tem:
+
+   NomeFunção ArgumentoA ArgumentoB ArgumentoC ...
+-}
+
+-- Strings e Caractéres
+"Texto entre abre áspas e fecha áspas define uma string"
+'a' -- Caractere
+'A' -- Caractere
+
+'Strings entre aspas simples sobe um erro' -- Erro léxico!
+
+-- Concatenação de Strings
+"StringA" ++ "StringB" -- "StringAStringB"
+
+-- Você pode listar uma string pelos seus caractéres
+"AbBbbcAbbcbBbcbcb" !! 0 -- 'A'
+"AbBbbcAbbcbBbcbcb" !! 1 -- 'b'
+"AbBbbcAbbcbBbcbcb" !! 2 -- 'B'
+
+----------------------------------------------------
+-- Listas e Túplas
+----------------------------------------------------
+
+-- A construção de uma lista precisa ser de elementos homogêneos
+[1, 2, 3, 4, 5] -- Homogênea
+[1, a, 2, b, 3] -- Heterogênea (Erro)
+
+-- Haskell permite que você crie sequências
+[1..5]
+
+{- Haskell usa avaliação preguiçosa o que
+   Permite você ter listas "infinitas"
+-}
+
+-- Uma lista "infinita" cuja razão é 1
+[1..]
+
+-- O 777º elemento de uma lista de razão 1
+[1..] !! 777 -- 778
+
+-- União de listas [lista_0] ++ [lista_1] ++ [lista_i]
+[1..5] ++ [6..10] ++ [1..4] -- [1,2,3,4,5,6,7,8,9,10,1,2,3,4]
+
+-- Adiciona um cabeçalho a sua lista e desloca a cauda
+0:[1..10] -- [0, 1, 2, 3, 4, 5]
+'a':['a'..'e'] -- "aabcde"
+
+-- Indexação em uma lista
+[0..] !! 5 -- 5
+
+-- Operadores de Listas usuais
+head ['a'..'e'] -- Qual o cabeçalho da lista ?
+tail ['a'..'e'] -- Qual a cauda da lista ?
+init ['a'..'e'] -- Qual a lista menos o último elemento ?
+last ['a'..'e'] -- Qual o último elemento ?
+
+-- list comprehensions
+[x*2 | x <- [1..5]] -- [2, 4, 6, 8, 10]
+
+-- with a conditional
+[x*2 | x <- [1..5], x*2 > 4] -- [6, 8, 10]
+
+-- Every element in a tuple can be a different type, but a tuple has a
+-- fixed length.
+-- A tuple:
+("haskell", 1)
+
+-- accessing elements of a tuple
+fst ("haskell", 1) -- "haskell"
+snd ("haskell", 1) -- 1
+
+----------------------------------------------------
+-- 3. Functions
+----------------------------------------------------
+-- A simple function that takes two variables
+add a b = a + b
+
+-- Note that if you are using ghci (the Haskell interpreter)
+-- You'll need to use `let`, i.e.
+-- let add a b = a + b
+
+-- Using the function
+add 1 2 -- 3
+
+-- You can also put the function name between the two arguments
+-- with backticks:
+1 `add` 2 -- 3
+
+-- You can also define functions that have no letters! This lets
+-- you define your own operators! Here's an operator that does
+-- integer division
+(//) a b = a `div` b
+35 // 4 -- 8
+
+-- Guards: an easy way to do branching in functions
+fib x
+  | x < 2 = x
+  | otherwise = fib (x - 1) + fib (x - 2)
+
+-- Pattern matching is similar. Here we have given three different
+-- definitions for fib. Haskell will automatically call the first
+-- function that matches the pattern of the value. 
+fib 1 = 1
+fib 2 = 2
+fib x = fib (x - 1) + fib (x - 2)
+
+-- Pattern matching on tuples:
+foo (x, y) = (x + 1, y + 2)
+
+-- Pattern matching on lists. Here `x` is the first element
+-- in the list, and `xs` is the rest of the list. We can write
+-- our own map function:
+myMap func [] = []
+myMap func (x:xs) = func x:(myMap func xs)
+
+-- Anonymous functions are created with a backslash followed by
+-- all the arguments.
+myMap (\x -> x + 2) [1..5] -- [3, 4, 5, 6, 7]
+
+-- using fold (called `inject` in some languages) with an anonymous
+-- function. foldl1 means fold left, and use the first value in the
+-- list as the initial value for the accumulator.
+foldl1 (\acc x -> acc + x) [1..5] -- 15
+
+----------------------------------------------------
+-- 4. More functions
+----------------------------------------------------
+
+-- currying: if you don't pass in all the arguments to a function,
+-- it gets "curried". That means it returns a function that takes the 
+-- rest of the arguments.
+
+add a b = a + b
+foo = add 10 -- foo is now a function that takes a number and adds 10 to it
+foo 5 -- 15
+
+-- Another way to write the same thing
+foo = (+10)
+foo 5 -- 15
+
+-- function composition
+-- the (.) function chains functions together.
+-- For example, here foo is a function that takes a value. It adds 10 to it,
+-- multiplies the result of that by 5, and then returns the final value.
+foo = (*5) . (+10)
+
+-- (5 + 10) * 5 = 75
+foo 5 -- 75
+
+-- fixing precedence
+-- Haskell has another function called `$`. This changes the precedence
+-- so that everything to the left of it gets computed first and then applied
+-- to everything on the right. You can use `.` and `$` to get rid of a lot
+-- of parentheses:
+
+-- before
+(even (fib 7)) -- true
+
+-- after
+even . fib $ 7 -- true
+
+----------------------------------------------------
+-- 5. Type signatures
+----------------------------------------------------
+
+-- Haskell has a very strong type system, and everything has a type signature.
+
+-- Some basic types:
+5 :: Integer
+"hello" :: String
+True :: Bool
+
+-- Functions have types too.
+-- `not` takes a boolean and returns a boolean:
+-- not :: Bool -> Bool
+
+-- Here's a function that takes two arguments:
+-- add :: Integer -> Integer -> Integer
+
+-- When you define a value, it's good practice to write its type above it:
+double :: Integer -> Integer
+double x = x * 2
+
+----------------------------------------------------
+-- 6. Control Flow and If Statements
+----------------------------------------------------
+
+-- if statements
+haskell = if 1 == 1 then "awesome" else "awful" -- haskell = "awesome"
+
+-- if statements can be on multiple lines too, indentation is important
+haskell = if 1 == 1
+            then "awesome"
+            else "awful"
+
+-- case statements: Here's how you could parse command line arguments
+case args of
+  "help" -> printHelp
+  "start" -> startProgram
+  _ -> putStrLn "bad args"
+
+-- Haskell doesn't have loops because it uses recursion instead.
+-- map applies a function over every element in an array
+
+map (*2) [1..5] -- [2, 4, 6, 8, 10]
+
+-- you can make a for function using map
+for array func = map func array
+
+-- and then use it
+for [0..5] $ \i -> show i
+
+-- we could've written that like this too:
+for [0..5] show
+
+-- You can use foldl or foldr to reduce a list
+-- foldl <fn> <initial value> <list>
+foldl (\x y -> 2*x + y) 4 [1,2,3] -- 43
+
+-- This is the same as
+(2 * (2 * (2 * 4 + 1) + 2) + 3)
+
+-- foldl is left-handed, foldr is right-
+foldr (\x y -> 2*x + y) 4 [1,2,3] -- 16
+
+-- This is now the same as
+(2 * 3 + (2 * 2 + (2 * 1 + 4)))
+
+----------------------------------------------------
+-- 7. Data Types
+----------------------------------------------------
+
+-- Here's how you make your own data type in Haskell
+
+data Color = Red | Blue | Green
+
+-- Now you can use it in a function:
+
+
+say :: Color -> String
+say Red = "You are Red!"
+say Blue = "You are Blue!"
+say Green =  "You are Green!"
+
+-- Your data types can have parameters too:
+
+data Maybe a = Nothing | Just a
+
+-- These are all of type Maybe
+Just "hello"    -- of type `Maybe String`
+Just 1          -- of type `Maybe Int`
+Nothing         -- of type `Maybe a` for any `a`
+
+----------------------------------------------------
+-- 8. Haskell IO
+----------------------------------------------------
+
+-- While IO can't be explained fully without explaining monads,
+-- it is not hard to explain enough to get going.
+
+-- When a Haskell program is executed, the function `main` is
+-- called. It must return a value of type `IO ()`. For example:
+
+main :: IO ()
+main = putStrLn $ "Hello, sky! " ++ (say Blue) 
+-- putStrLn has type String -> IO ()
+
+-- It is easiest to do IO if you can implement your program as 
+-- a function from String to String. The function 
+--    interact :: (String -> String) -> IO ()
+-- inputs some text, runs a function on it, and prints out the 
+-- output.
+
+countLines :: String -> String
+countLines = show . length . lines
+
+main' = interact countLines
+
+-- You can think of a value of type `IO ()` as representing a
+-- sequence of actions for the computer to do, much like a
+-- computer program written in an imperative language. We can use
+-- the `do` notation to chain actions together. For example:
+
+sayHello :: IO ()
+sayHello = do 
+   putStrLn "What is your name?"
+   name <- getLine -- this gets a line and gives it the name "name"
+   putStrLn $ "Hello, " ++ name
+   
+-- Exercise: write your own version of `interact` that only reads
+--           one line of input.
+   
+-- The code in `sayHello` will never be executed, however. The only
+-- action that ever gets executed is the value of `main`. 
+-- To run `sayHello` comment out the above definition of `main` 
+-- and replace it with:
+--   main = sayHello
+
+-- Let's understand better how the function `getLine` we just 
+-- used works. Its type is:
+--    getLine :: IO String
+-- You can think of a value of type `IO a` as representing a
+-- computer program that will generate a value of type `a` 
+-- when executed (in addition to anything else it does). We can
+-- store and reuse this value using `<-`. We can also 
+-- make our own action of type `IO String`:
+
+action :: IO String
+action = do
+   putStrLn "This is a line. Duh"
+   input1 <- getLine 
+   input2 <- getLine
+   -- The type of the `do` statement is that of its last line.
+   -- `return` is not a keyword, but merely a function 
+   return (input1 ++ "\n" ++ input2) -- return :: String -> IO String
+
+-- We can use this just like we used `getLine`:
+
+main'' = do
+    putStrLn "I will echo two lines!"
+    result <- action 
+    putStrLn result
+    putStrLn "This was all, folks!"
+
+-- The type `IO` is an example of a "monad". The way Haskell uses a monad to
+-- do IO allows it to be a purely functional language. Any function that
+-- interacts with the outside world (i.e. does IO) gets marked as `IO` in its
+-- type signature. This lets us reason about what functions are "pure" (don't
+-- interact with the outside world or modify state) and what functions aren't.
+
+-- This is a powerful feature, because it's easy to run pure functions
+-- concurrently; so, concurrency in Haskell is very easy.
+
+
+----------------------------------------------------
+-- 9. The Haskell REPL
+----------------------------------------------------
+
+-- Start the repl by typing `ghci`.
+-- Now you can type in Haskell code. Any new values
+-- need to be created with `let`:
+
+let foo = 5
+
+-- You can see the type of any value with `:t`:
+
+>:t foo
+foo :: Integer
+
+-- You can also run any action of type `IO ()`
+
+> sayHello
+What is your name?
+Friend!
+Hello, Friend!
+
+```
+
+There's a lot more to Haskell, including typeclasses and monads. These are the big ideas that make Haskell such fun to code in. I'll leave you with one final Haskell example: an implementation of quicksort in Haskell:
+
+```haskell
+qsort [] = []
+qsort (p:xs) = qsort lesser ++ [p] ++ qsort greater
+    where lesser  = filter (< p) xs
+          greater = filter (>= p) xs
+```
+
+Haskell is easy to install. Get it [here](http://www.haskell.org/platform/).
+
+You can find a much gentler introduction from the excellent
+[Learn you a Haskell](http://learnyouahaskell.com/) or
+[Real World Haskell](http://book.realworldhaskell.org/).