multisubs.swift

extension CollectionType {
  subscript(i1: Index, i2: Index, rest: Index...) -> PermutationGenerator<Self, [Self.Index]> {
    get {
      return PermutationGenerator(elements: self, indices: [i1, i2] + rest)
    }
  }
}

extension Array {
  subscript(i1: Index, i2: Index, rest: Index...) -> [T] {
    get {
      return ([i1, i2] + rest).map{self[$0]}
    } set(vals) {
      for (ind, val) in zip([i1, i2] + rest, vals) {
        self[ind] = val
      }
    }
  }
}