anchor.diff:      File.WriteAllText(fout, content)
       () 
   
  +
   // is this a post?  check the filename
   let is_post (page:Page) = 
       page.FileName.IndexOf("_posts") <> -1
  -
   
   // get the next post.
   let get_next_post (page:Page) (posts:IEnumerable<Page>) = 
  
positive.code: 
      let output_dir = config.OutputDir
      let source_dir = config.SourceDir
      // setup output folder
      if Directory.Exists(output_dir) = false then
          Directory.CreateDirectory(output_dir) |> ignore
  
negative.code:         let head = prevposts |> Seq.head
          let pprev = prevposts |> Seq.fold acc head
          pprev
      with
      |_ -> new Page()
  
  