anchor.diff:          eval("packageDescription(\"" + packageName + "\")$Description").GetValue()
   
       let getFunctionDescriptions packageName : Map<string, string> =
  -        RSafe <| fun () ->
           exec <| sprintf """rds = readRDS(system.file("Meta", "Rd.rds", package = "%s"))""" packageName
           Map.ofArray <| Array.zip ((eval "rds$Name").GetValue()) ((eval "rds$Title").GetValue())
   
       let private packages = System.Collections.Generic.HashSet<string>()
   
       let loadPackage packageName : unit =
  -        RSafe <| fun () ->
           if not(packages.Contains packageName) then
               if not(eval("require(" + packageName + ")").GetValue()) then
                   failwithf "Loading package %s failed" packageName
  
positive.code:     let namedParams (s: seq<string*_>) = dict <| Seq.map (fun (n,v) -> n, box v) s
  
  module internal RInteropInternal =
      let interopLock = "RProvider.RInterop.lock"
      let RSafe f =
          lock interopLock f
  
      type RParameter = string
      type HasVarArgs = bool
  
  
negative.code:         | _ ->                      None
  
      let internal defaultConvertFromR (sexp: SymbolicExpression) : obj =
          let converters = mefContainer.Value.GetExports<IDefaultConvertFromR>()
          match converters |> Seq.tryPick (fun conv -> conv.Value.Convert sexp) with
          | Some res  -> res
  