scalaformonad

val usdQuote = Future { connection.getCurrentValue(USD) }
val chfQuote = Future { connection.getCurrentValue(CHF) }
val purchase = for {
  usd <- usdQuote
  chf <- chfQuote
  if isProfitable(usd, chf)
} yield connection.buy(amount, chf)
purchase onSuccess {
  case _ => println("Purchased " + amount + " CHF")
}

// is the same as

val purchase = usdQuote flatMap {
  usd =>
  chfQuote
    .withFilter(chf => isProfitable(usd, chf))
    .map(chf => connection.buy(amount, chf))
}