anchor.diff:  
     /// Concatenates the given documents with a `linebreak` in between.  `lhs <..>
     /// rhs` is equivalent to `lhs <^> linebreak <^> rhs`.
  +#if DOC
  +  ///
  +  /// For example
  +  ///
  +  ///> txt "a" <..> txt "b"
  +  ///
  +  /// renders as
  +  ///
  +  ///> a
  +  ///> b
  +  ///
  +  /// and
  +  ///
  +  ///> group (txt "a" <..> txt "b")
  +  ///
  +  /// renders as
  +  ///
  +  ///> ab
  +#endif
     static member (<..>): Doc * Doc -> Doc
   
     /// Concatenates the given documents with a `softbreak` in between.  `lhs <//>
  
positive.code:   /// onto a single line or onto multiple lines using line continuation
    /// characters.
    ///
    /// Given
    ///
    ///> let wide = txt "\\\"a\\nb\\nc\\\""
    ///> let narrow = vsep [txt "\"a\\n\""; txt "\"b\\n\""; txt "\"c\""]
  
negative.code:   static member (<^>): Doc * Doc -> Doc
  
    /// Concatenates the given documents with a `space` in between.  `lhs <+> rhs`
    /// is equivalent to `lhs <^> space <^> rhs`.  For example, `txt "a" <+> txt
    /// "b"` renders as `a b`.
    static member (<+>): Doc * Doc -> Doc
  
    /// Concatenates the given documents with a `line` in between.  `lhs <.> rhs`
    /// is equivalent to `lhs <^> line <^> rhs`.
  #if DOC
    ///
    /// For example
    ///
    ///> txt "a" <.> txt "b"
    ///
    /// renders as
    ///
    ///> a
    ///> b
    ///
    /// and
    ///
    ///> group (txt "a" <.> txt "b")
    ///
    /// renders as
    ///
    ///> a b
    ///
    /// Note: In the original Haskell libraries, the symbol <$> was used for this
    /// operation, but it is not a legal symbol in F#.
  #endif
    static member (<.>): Doc * Doc -> Doc
  
  