       _base: _base.generate(), _transform: _transform)
   }
 
-  var _base: Base
-  var _transform: (Base.Generator.Element)->T
+  public var _base: Base
+  internal var _transform: (Base.Generator.Element)->T
 }
 
 //===--- Collections ------------------------------------------------------===//

    return _base.underestimateCount()
  }

  var _base: Base
  var _transform: (Base.Generator.Element)->T
}



  public typealias Distance = Base.Distance
  
  public init(_ base: Base) { self._base = base }
  public let _base: Base

  /// Return the minimum number of applications of `successor` or
  /// `predecessor` required to reach `other` from `self`.
