anchor.diff:              let filteredAccepts = filterSortAccept accepts 
               negotiateList matchCharset serves filteredAccepts
   
  +/// <summary>
  +/// Intersects accepted and served charsets.
  +/// Returns the preferred viable charset, or <c>None</c>.
  +/// </summary>
  +/// <param name="x"></param>
   let bestCharset x = bestOf negotiateCharset x
   
  
positive.code:             then None
              else Some serves
  
  let negotiateLanguage x = negotiate matchLanguage x
  let bestLanguage x = bestOf negotiateLanguage x
  
  let matchCharset serves accepts =
      match serves,accepts with
      | "*",a -> Some a
  
negative.code:     List.tryFind isMatch accepts
      |> Option.map ignore
  
  /// <summary>
  /// Matches two language tags
  /// </summary>
  /// <param name="serves"></param>
  /// <param name="accepts"></param>
  let matchLanguage serves accepts =
      match serves,accepts with
      | "*",a -> Some a
  