anchor.diff:  open YC.FSA.FsaApproximation
   open YC.FSA.GraphBasedFsa
   
  -let lexerErrMsg = "Unexpected symbol: "
  -let parserErrMsg = "Syntax error. Unexpected token "
  -let undefinedVariableErrMsg = "undefined variable"
  +let lexerErrMsg = "Unexpected symbol:"
  +let parserErrMsg = "Syntax error. Unexpected token"
  +let undefinedVariableErrMsg = "Undefined variable"
   
   type DrawingGraph (vertices : IEnumerable<int>, edges : ResizeArray<TaggedEdge<int, string>>) =
       member this.Vertices = vertices
  
positive.code:     inherit System.EventArgs()
      member this.Lang = lang
  
  type TreeGenerationState<'node> = 
      | Start
      | InProgress of 'node * AstNode list
      | End of 'node
  
  exception LexerException of string * obj
  
  
negative.code:                 |> Array.map 
                      (
                          function 
                              Smbl (char, position) -> (sprintf "%s %c" lexerErrMsg char), position |> getDocumentRange 
                              | e -> failwithf "Unexpected tokenization result: %A" e
                      )
                  |> Array.iter addLError 
  