The container classes included in the C++ standard library serve as good illustrations of both the strengths and the weaknesses of the language. The strengths are obvious: efficient, type-safe containers with performance guarantees suitable for a huge variety of applications. And the weaknesses? Compiler error messages that redefine the term useless, and documentation that makes a mockery of the word.

In this article I’ll illustrate how you might bump into these problems using the unordered_map container, as well showing you how to work past the problems. By rights this basic hash map should be the first- or second-most used container in your arsenal, but if you are less than a C++ savant, you might find yourself ditching it out of frustration.
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One of the great things about C, and even more so for C++, is its strong type checking mechanisms. In general a lot of bugs are caught at compile time, and experienced programmers are able to recognize and fix these types of errors quickly.

Unfortunately, there are plenty of places in any C program where type checking disappears. The GNU C compiler, gcc, goes above and beyond the call of duty to help in these areas. But sometimes that help can be a can of worms all of its own.
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In my last post I showed a particularly easy way to to set up an SMTP server so postfix could send mail from your Linux system. In this post I’m going to add a few tips that might help you get through some rough spots in the whole process.
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Getting a new computer can be interesting. My recent purchase of a Dell XPS notebook came with a few problems that I didn’t anticipate, including:

• The video hardware is not properly supported under Linux – my fault for not checking up on this.
• The backlit keyboard is an ergonomic catastrophe. When viewed under bright light, the translucent legends on light brown keycaps literally disappear. I got Dell to replace this with a non-backlit keyboard, problem solved.
• The traditional numeric keypad control keys, including arrows, Page Up/Down, Delete, and Home, have all been reduced in size and moved to random new locations. Since the notebook I bought is the size of a small car there was really no good reason for this, and it will probably take six months for my fingers to get used to the new locations.
• Under Windows, the Bluetooth driver has some sort of glitch that causes Word to crash – go figure that one out. This was resolved by disabling an addin that I wasn’t likely to ever use anyway.
• Under Linux the Bluetooth driver makes my wireless mouse nearly unusable. However, turning off Bluetooth also turns off wireless networking. I feel like there is a solution to this out there somewhere, I just have to find it.

None of these problems are going to ruin my life, but they definitely contributed to a small feeling of buyer’s remorse which I am still trying to shake off.
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For most of the thirty-some years that I’ve been paid to program, I’ve worked with Assembly language, C, or C++. There have been some diversions to Java, which is pretty painless for a C++ programmer, and always the odd short job or two in anything from Perl to Haskell.

But for the last three months or so I’ve been working full time on a short-timeline project that is using PHP as a general-purpose scripting language. So I’ve been working in this unfamiliar language at a fairly frantic pace, and I have to say that PHP, like Perl, is a strange place for a C programmer.
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Back in the day the Sapir-Whorf hypothesis was all the rage in the study of linguistics. With apologies to those who actually work in the field, I’ll crudely summarize it as the idea that the language you speak both constrains and influences how you think. The idea says that if your language only has one word for snow, for example, you will actually have a hard time seeing any difference between light powder and crunchy ice pack.

Sapir-Whorf was seen as completely discredited back when I learned about it, and while Linguistic Relativity has enjoyed a slight comeback with a weakly restated set of hypotheses, it seems fairly certain that human thought is by no means confined to a cage built out of vocabulary and grammar.

Our field has long had its own Sapir in E.W. Dijkstra, whoe spelled it out with money quotes like these:
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Edsger W. Dijkstra wrote an influential paper back in 1988 called On the cruelty of really teaching computing science, which advocated an approach strongly grounded in the study of formal systems.

While I would be the first to admit that I am not fit to carry the late Dr.’s punch cards, I would say that if he really wanted to see cruelty, he might have tried his hand at the undergraduate course I taught this semester: C/C++ Programming in a UNIX Environment. This class was cruelty personified.
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If I had been drawing a paycheck for every hour I spent working on Project Euler’s problem 328, I think my summer vacation would already be paid for. But instead, after a long ten days or so of distraction, I’ll have to settle for the satisfaction of being number 38 or 39 to solve it.
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When I finally wrapped up the mathematical modeling of the k-consecutive heads coin toss problem I had a concise formula:

To calculate the chances of k heads in a row appearing in n tosses, I just had to calculate a k-step Fibonacci number, and then divide it by an exponent of 2, and subtract the result from 1. Not complicated at all – but there was one catch. After a million coin tosses, the Fibonacci number and the exponent of 2 were approximately 300,000 digits long – way outside the scope of normal computations in languages like C++ and Java.

To get the exact result I needed, I used the BigInteger and BigDecimal Java classes to handle those big numbers, and had to wait about an hour to get the result. As it turns out, there is a much faster and easier way to do things
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Photo by Nick Richards

Ken Olsen, founder of Digital Equipment Corporation, died Sunday, February 6 at the age of 84.
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