code: private static Processor getProcessor(Opcode opcode) {
  		switch (opcode) {
  		case NOT_EMPTY:
  			return NOT_EPMTY_PROCESSOR;
  
  		case EQUALS:
  			if (EQUALS_PROCESSOR == null) {
  				EQUALS_PROCESSOR = new EqualsProcessor();
  			}
  			return EQUALS_PROCESSOR;
  
  		case LESS_THAN:
  			if (LESS_THAN_PROCESSOR == null) {
  				LESS_THAN_PROCESSOR = new LessThanProcessor();
  			}
  			return LESS_THAN_PROCESSOR;
  
  		case GREATER_THAN:
  			if (GREATER_THAN_PROCESSOR == null) {
  				GREATER_THAN_PROCESSOR = new GreaterThanProcessor();
  			}
  			return GREATER_THAN_PROCESSOR;
  
  		default:
  			throw new BugError("Unsupported opcode |%s|.", opcode);
  		}
  	}
docs: Operator processor factory. Returned processor instance is a singleton, that is, reused on running virtual machine.
  
  @param opcode return processor suitable for requested operator.
  @return operator processor instance.