anchor.diff:  
   /// Extensions for F#'s Map module.
   module Map =
  +    /// <summary>
  +    /// Returns a new map made from the given Dictionary (or anything else that implements <code>seq&lt;KeyValuePair&lt;&apos;a, &apos;b&gt;&gt;</code>).
  +    /// </summary>
  +    let ofDict (d:seq<KeyValuePair<'a, 'b>>) =
  +        d |> Seq.map (fun (KeyValue(x,y)) -> x, y) |> Map.ofSeq
  +
       let spanWithKey pred map =
           map
           |> Map.fold (fun (l,r) k v ->
  
positive.code:     let valueList map = map |> Map.toList |> List.unzip |> snd
  
      /// Combines the two Maps into a single Map
      let union (loses: Map<_,_>) (wins: Map<_,_>) = 
          Seq.fold (fun m (KeyValue(k,v)) -> Map.add k v m) loses wins
  
      let choose (f : 'T -> 'b -> 'c option) (map : Map<'T,'b>) =
          (Map.empty, map) ||> Map.fold (fun s k v -> 
  
negative.code:         choose chooser table
  
      /// Compares two maps for equality using the given comparison function, element by element.
      let inline equalsWith (eq : 'k -> 'v -> 'k -> 'v -> bool) (xs:Map<'k, 'v>) (ys:Map<'k, 'v>) =
          let eq' (k1, v1) (k2, v2) = eq k1 v1 k2 v2
          let xs' = Map.toSeq xs
          let ys' = Map.toSeq ys
          Seq.equalsWith eq' xs' ys'
  
  
  #if FX_PORTABLE
  