title: Why NSNotFound isn't -1 but NSIntegerMax
body: <p>NSNotFound is defined as NSIntegerMax, which has different values on 32-bit and 64-bit, this brings a lot of inconvenience for persistent and distributed env. Why not define it as -1? </p>
  
  <p>PS, In ObjC and Cocoa, some indexOf... methods returns NSNotFound but some returns -1, is there a reason these results are inconsistent.</p>