anchor.diff:  module NonEmptySeq =
       /// <summary>Builds a non empty sequence from the given sequence.</summary>
       /// <param name="seq">The input sequence.</param>
  -    /// <returns>Non empty sequence containing the elements of the list.</returns>
  +    /// <returns>Non empty sequence containing the elements of the original sequence.</returns>
       /// <remarks>
       ///   **This function does not check whether the sequence is actually non empty or not.**
       /// 
  
positive.code:             }
          go head state |> unsafeOfSeq
  
      /// <summary>Combines the two sequences into a list of pairs. The two sequences need not have equal lengths:
      /// when one sequence is exhausted any remaining elements in the other
      /// sequence are ignored.</summary>
      ///
  
negative.code: 
      /// <summary>Builds a non empty sequence from the given sequence.</summary>
      /// <param name="seq">The input sequence.</param>
      /// <returns>Non empty sequence containing the elements of the sequence.</returns>
      /// <exception cref="System.ArgumentException">Thrown when the input sequence is empty.</exception>
      /// <remarks>
      ///   Throws exception for empty sequence.
  