Programming Topics

Look at the following code and decide what is wrong with it. When you have done so, decide what it has to do with the previous section in particular and this section of C Vu in general - well actually the whole of your life.

There have been many languages for writing applications, but relatively few foundation platforms which support applications that are written in various different languages. We've had assembler (proprietary), then C (an ISO standard), and now we have the Common Language Infrastructure (CLI). The CLI standard is ISO/IEC 23271; the same content is also available online at http://www.ecma-international.org/publications/standards/Ecma-335.htm.

Files form the raw ingredients of a software system - source files, build files, configuration files, resource files, scripts etc. These files are organised into directories.

“There is more to life than increasing its speed” - Mahatma Gandhi

We live in a fast food culture. Not only must our dinner arrive yesterday, our car should be fast, and our entertainment instant. Our code should also run like lightning. I want my result. And I want it now.

Ironically, writing fast programs takes a long time.

Optimisation is a spectre hanging over software development, as W.A. Wulf observed. “More computing sins are committed in the name of efficiency (without necessarily achieving it) than for any other single reason – including blind stupidity”.

It’s a well-worn subject, with plenty of trite soundbites bounding around, and the same advice being served time and time again. But despite this, a lot of code is still not developed sensibly. Programmers get sidetracked by the lure of efficiency and write bad code in the name of performance.

In these articles we’ll address this. We’ll tread some familiar ground and wander well-worn paths, but look out for some new views on the way. Don’t worry – if the subject’s optimisation it shouldn’t take too long...

What can be said about C’s everyday do...while loop? It just does something while some condition holds. End of story, right?

No, of course not. That would make the title of this small article silly, so let’s cover two topics.

We have all seen comments in source files which look more like executable code than documentation.

The first line in the body of the for loop below is such a comment: you might expect to be able to remove the leading slashes and have code which compiles and runs, but functions slightly differently.

What did the author of this comment intend?

Example 0

for (Surfaces::iterator sf = surfaces.begin();
     sf != surfaces.end();
     ++sf) {
  // std::cout << "Drawing: " << *sf << "\n";
  sf->draw();
}

OK, I’m being disingenuous. I’m aware that the comment isn’t really a comment, it’s commented-out code. And, like any tolerant and capable programmer, by examining the surrounding context I can guess why this code has been commented out.

This article examines how to comment out code, then describes various problems which lead to code being commented out, before finally arguing that there’s often a better solution to these problems.

The first step here in finding problems in the code is to identify the problem the code is trying to solve. The discussion in the C Vu article is basically about curiosities in the way in which the C++ standard library std::istream is defined, but I will make the perhaps unwarranted assumption that what the problem the code is really about is not the uses of std::istream, but rather, more generally, how to write a read routine that can effectively and safely capture data from an input stream. Actually as the first problem below illustrates neither of these issues can be effectively addressed without the other.