anchor.diff:      ;
   
   performanceOperationDecl
  -    :   OPERATION name=IDENTIFIER operationParameterList (COLON programNamedType)? SEMICOLON
  -        (affectsClause)?
  -        (requiresClause)?
  -        (ensuresClause)?
  +    :   operationDecl
           (durationClause)?
           (manipulationDispClause)?
       ;
  
positive.code:     ;
  
  operationProcedureDecl
      :   OPERATION
          name=IDENTIFIER operationParameterList SEMICOLON
          (affectsClause)?
          (requiresClause)?
          (ensuresClause)?
          PROCEDURE
          (facilityDecl)*
          (variableDecl)*
  
negative.code:     ;
  
  recursiveOperationProcedureDecl
      :   operationDecl
          RECURSIVE PROCEDURE
          decreasingClause
          (facilityDecl)*
  