anchor.diff:      parseBinaryExpressionLevel parseAndExpression
           [ ("||", Or) ]
   
  -do parseExpressionRef := parseOrExpression
  +do parseExpressionRef := parseOrExpression <?> "expression"
   
   
   (*
  
positive.code: let pipe3ws x y z f = pipe3 (x .>> ws) (y .>> ws) (z .>> ws) f
  
  /// Parses an identifier.
  let parseIdentifier = many1Chars2 (pchar '_' <|> asciiLetter)
                                    (pchar '_' <|> asciiLetter <|> digit)
  
  
  // Bracket parsers.
  
negative.code: ///     </para>
  /// </summary>
  let parseSymbolic =
      (pipe2ws
          (pstring "%" >>. inBraces parseSymbolicSentence)
          (parseParamList parseExpression)
          (fun s es -> { Sentence = s; Args = es })) <?> "symbolic"
  
  /// Parser for primary expressions.
  let parsePrimaryExpression =
  