anchor.diff:  
   /// The abstract type of documents.
   type [<Sealed; NoEquality; NoComparison>] Doc =
  -  /// `lhs <^> rhs` is the concatenation of the documents `lhs` and `rhs`.
  +  /// `lhs <^> rhs` is the concatenation of the documents `lhs` and `rhs`.  For
  +  /// example, `txt "a" <^> txt "b"` renders as `ab`.
   #if DOC
     ///
     /// Note: This is the same as the operator `<>` used in the original Haskell
  
positive.code:   /// renders as
    ///
    ///> a b
  #endif
    val group: Doc -> Doc
  
  
negative.code: 
    // == Basic Combinators ==
  
    /// The `empty` document is equivalent to `txt ""`.
    val empty: Doc
  
    /// `chr c` renders to the character `c`.  The character shouldn't be a
  