C++ const Correctness
As a general principle of class design, encapsulation is good. It reduces the complexity of your code and reduces the number of possible interactions between classes. Using const member functions increases encapsulation by restricting the ways in which an object can be used in certain circumstances, particularly when objects are passed by constant reference to functions or member functions. The const modifier is evaluated at compile-time, so it costs nothing at run-time.
You now have the tools required to make your classes const correct. A proper const interface allows the compiler to do a lot of type-checking work for you in situations where constant objects are used. Without a const interface, the speed and encapsulation benefits of constant user-defined types is lost. A class designed without const member functions hamstrings those who would use the class, as there otherwise would be no way to use the class when objects of its type are passed by const references. As shown above, users of your classes have good reason to manipulate them in this way. Being const correct then comes full-circle, as only the const interface to your class is available in these situations.
Many programming practices and conventions are available that can improve code in all types of ways. The notion of const, though, is supported directly by the language and provides a free compile-time mechanism to better encapsulate the concepts within your programs as classes. The most fundamental unit of design in C++ is the class. Concise, simple and const correct class interfaces improve portability, add flexibility and provide a foundation for extending your design to previously unforeseen purposes.
The public interfaces of your classes are the ones used by developers, including yourself. Interfaces that exploit the value of const modifiers promote looser coupling between classes by further limiting the public interface. Looser coupling provides a better foundation for expanding and re-tooling your classes for future situations. Designing for future changes is essential, and const correctness is an important principle to follow in future-proofing your class designs today.
Dave Berton is a professional programmer. He can be reached at firstname.lastname@example.org.
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
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With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide