Notes from effective scala

• Use expressions, not statements(telling the computer what to do)
• Don’t tell it how to

// Don't do this
def findPeopleIn(city: String, 
                 people: Seq[People]): Set[People] = {
  val found = new Mutable.HashSet[People]
  for (person <- people) {
      for (address <- person.addresses) { 
          if(address.city == city
              found.put(person)
      }
  }
  return found
}
// do this
def findPeopleIn(city: String,
    people: Seq[People]): Set[People] = 
    for {
        person <- people.toSet[People],
        address <- person.addresses
        if address.city == city
    } yield person

• Mutable safe code
  • use Vector instead of Arrays