anchor.diff:  ;
   // R1101
   mainProgram : 
  -  (   programStmt   )?  
  -  (   specificationPart   )?  
  -  (   executionPart   )?  
  -  (   internalSubprogramPart   )?  
  +  programStmt  
  +  specificationPart  
  +  executionPart  
  +  internalSubprogramPart  
   endProgramStmt
   ;
   // R1103
  
positive.code: // R709
  addOp : 
   PLUS 
  | 
  ;
  // R461
  enumDefStmt : 
  
negative.code: // R1231
  subroutineSubprogram : 
  subroutineStmt
    specificationPart 
    executionPart
    internalSubprogramPart
  endSubroutineStmt
  ;
  // R1230
  