title: Data strucure used in Swift Var and internal mapping of var to types
body: <p>I am a beginner to Swift</p>
  
  <p>In Objective we have independent types where they have their Data structure.
  For example: NsArray, NsDictionary will have their own own data structure to store values.</p>
  
  <p>What about Swift Var, if I don't explicitly specify the type of variable it will automatically assume it is a NSArray if array values are passed to it.</p>
  
  <p>How will it distinguish between NsArray and NSMutableArray here?
  Probably I got a solution for this which is let for immutable and var for mutable.</p>
  
  <p>And how will the internal mapping of var to specific type happens?
  Will the mapping happen at Run time? Will this cause slowness in my code if I don't specify the type explicitly?</p>
  
  <p>And will let act as final in Swift?</p>