anchor.diff:          List.choose chooser.Invoke l
   
       [<Extension>]
  +    static member TryFind (l, pred: _ Predicate) = 
  +        List.tryFind pred.Invoke l
  +
  +    [<Extension>]
  +    static member TryFind (l, value) = 
  +        List.tryFind ((=) value) l
  +
  +    [<Extension>]
       static member Cons (l, e) = e::l
   
       static member Create([<ParamArray>] values: 'a array) =
  
positive.code: [<Extension>]
  type FSharpChoice =
  
      [<Extension>]
      static member Match (c, f1: Func<_,_>, f2: Func<_,_>) =
          match c with
  
negative.code: 
  type FSharpLazy = 
      static member Create (v: _ Func) = Lazy.Create v.Invoke
      static member CreateFromValue v = Lazy.CreateFromValue v