val first = List(1, 2)
val next = List(8, 9)

for {
  i <- first
  j <- next
}
yield(i * j)

// gets converted to

first flatMap {
  f => next map {
    n => f * n
  }
}

// List is a monad
// The 2 statements in the for comprehension act as generators for the lists
// Each pair generated is sequenced through the flatMap (which is Scala's bind) to generate the product