anchor.diff:    module Prototype = 
   
       /// Implements: 15.4.4.4 Array.prototype.concat ( [ item1 [ , item2 [ , … ] ] ] )
  -    let concat (func:FO) (this:CO) (args:Args) =
  +    let private concat (func:FO) (this:CO) (args:Args) =
         let a = func.Env.NewArray(uint32 args.Length)
   
         let rec concat (n:uint32) (c:BV) (i:int) =
  
positive.code:       double n
  
      /// Implements: 15.4.4.9 Array.prototype.shift ( )
      let shift (func:FO) (this:CO) =
        let length = this.GetLength()
  
        // Length = 0, put length and return undefined
  
negative.code:       concat 0u (BV.Box this) 0
  
      /// Implements: 15.4.4.5 Array.prototype.join (separator)
      let private join (func:FO) (this:CO) (separator:BV) =
        let length = this.GetLength()
        let separator =
          match separator.Tag with
  