ilyannn

Instead of

assert(!array.isEmpty, "Array guaranteed to be non-empty because...")
let lastItem = array.last!

guard !array.isEmpty 
    else { fatalError("Array guaranteed to be non-empty because...") }

// ... etc ...

ilyannn

// TODO: insert guards to use open-source version of random() if necessary

func random(x: Int) -> Int {
    return Int(arc4random_uniform(UInt32(endBoundary)))
}

extension CollectionType {
    
    /// create a lazy succession of randomly ordered indices
    ///

ilyannn

//Filter.swift 
  
  public mutating func next() -> Base.Element? {
    var n: Base.Element?
    for/*ever*/;; {
      n = _base.next()
      if n != nil ? _predicate(n!) : true {
        return n
      }
    }

ilyannn

enum StringPaddingStyle {
    case Left, Right
}

func padString(source: String, 
        with character: Character = " ",
        fill target: Int, 
        style: StringPaddingStyle = .Left
    ) -> String {