diegopacheco

import Data.Char (toUpper)

up :: [Char] -> [Char] 
up s = [toUpper c | c <- s]

diegopacheco

boomBangs xs = [ if x < 10 then "BOOM!" else "BANG!" | x <- xs, odd x]  

boomBangs [7..13] -- ["BOOM!","BOOM!","BANG!","BANG!"]

diegopacheco

def even(from: Int, to: Int): List[Int] = for (i <- List.range(from, to) if i % 2 == 0) yield i

Console.println(even(0, 20)) // List(0, 2, 4, 6, 8, 10, 12, 14, 16, 18)

diegopacheco

 for (i <- Iterator.range(0, 20);
      j <- Iterator.range(i + 1, 20) if i + j == 32)
           println("(" + i + ", " + j + ")")

// (13, 19)
// (14, 18)
// (15, 17)

diegopacheco

for(  x  <-  ( 1 to 5 )  ) yield x*x  // scala.collection.immutable.IndexedSeq[Int] = Vector(1, 4, 9, 16, 25)

diegopacheco

Just 5 >>= (\ x -> if (x == 0) then fail "zero" else Just (x + 1) )   -- Just 6

Just 0 >>= (\ x -> if (x == 0) then fail "zero" else Just (x + 1) ) -- Nothing

Nothing >>= (\ x -> if (x == 0) then fail "zero" else Just (x + 1) ) -- Nothing

diegopacheco

def funcMonadic[A](f1: () => A) = new {
	 def andThen28[B](f2: () => B) = { f1() ; f2() }
}
  
def monadic[A](f1: () => A) = new {
   def ->[B](f2: () => B) = { f1() ; f2() }
}
  
def bigMonadicPipe() = {
   monadic( () => print("A") ) -> ( () => print("B") ) -> ( () => print("C") )()

diegopacheco

fmap (++"!") (Just "wisdom") -- Just "wisdom!"

fmap (++"!") Nothing  -- Nothing


applyMaybe :: Maybe a -> (a -> Maybe b) -> Maybe b  
applyMaybe Nothing f  = Nothing  
applyMaybe (Just x) f = f x 

Just "smile" `applyMaybe` \x -> Just (x ++ " :)")  -- Just "smile :)" 

diegopacheco

class Monad m where  
    return :: a -> m a  
  
    (>>=) :: m a -> (a -> m b) -> m b  
  
    (>>) :: m a -> m b -> m b  
    x >> y = x >>= \_ -> y  
  
    fail :: String -> m a  
    fail msg = error msg 

diegopacheco

instance Monad Maybe where  
    return x = Just x  
    Nothing >>= f = Nothing  
    Just x >>= f  = f x  
    fail _ = Nothing