anchor.diff:  
   open Gen
   
  +///Extension methods to build generators - contains among other the Linq methods.
   [<System.Runtime.CompilerServices.Extension>]
   type GeneratorExtensions = 
       ///Map the given function to the value in the generator, yielding a new generator of the result type.  
  
positive.code:     static member OfSize (sizedGen : Func<int,Gen<_>>) =
          sized <| fun s -> (sizedGen.Invoke(s))
  
  
  type Shrink =
      ///Returns the immediate shrinks for the given value based on its type.
      static member Type<'a>() = shrink<'a>
  
  //mutable counterpart of the Config type
  type Configuration() =
      let mutable maxTest = Config.Quick.MaxTest
      let mutable maxFail = Config.Quick.MaxFail
  
negative.code:         SpecBuilder<'a,'b,'c>( generator0, shrinker0, generator1, shrinker1,generator2, shrinker2, 
              (fun a b c -> (assertion0 a b c) .|. (label name (assertion.Invoke(a,b,c)))), conditions, collects, classifies)  
        
  ///Entry point to specifying a property.
  type Spec private() =
      static let _ = Runner.init.Value
      static let noshrink = fun _ -> Seq.empty
      static member ForAny(assertion:Func<'a,bool>) =
  