HashableSequence.swift

extension SequenceType where Generator.Element: Hashable {
  
  var uniques: [Generator.Element] {
  
    var past = Set<Generator.Element>()
    
    return self.filter {
      element in
      if past.contains(element) {
        return false
      } else {
        past.insert(element)
        return true
      }
    }
  }
  
  var freqs: [Generator.Element:Int] {
    var accu: [Generator.Element:Int] = [:]
    for element in self { accu[element] = accu[element]?.successor() ?? 1 }
    return accu
  }
}