Old computer science books aren’t perceived as being of much use, since everything is so much better now. Of course, that’s not entirely true, especially when we are interested in the techniques used in the days where 32KB core memory was “a lot”. Leafing through one such book, Standish’s 1980 Data Structure Techniques, I found a method of maintaining doubly-linked lists using only one pointer. Let’s see how it works!
As I’ve mentioned before, my new job will ask me to program more in Python than C++, and that’s some what new for me. Of course, I’ve criticized Python’s dismal performance on two occasions, getting me all kind of comments (from “you can’t compare performance like that!” to “use another language then” passing by “bind to external high-performance libraries”).
But it seems that my mastery of Python is still quite inadequate, and yesterday (at the time of writing, anyway) I discovered how Python’s by-reference parameters work. Unlike C or C++ that use explicit syntax to specify what kind of object we’re dealing with (either by value, pointer, or by reference), Python is a bit sneaky.
If you code a lot in a week, you’re bound to make some (possibly) amusing typos. Almost every time, the typo is detected by the compiler and an error is issued, but sometimes you manage to (mis)type valid code! And I recently make one of those typo and I started wondering how far we can push this idea in writing really, really, really, really ugly code.
The C (and C++) preprocessor is a powerful but dangerous tool. For sure, it helps with a number of problems, from conditional code inclusion to explicit code generation, but it has a few problems. In fact, more than a few. It is evil.
The C preprocessor (hereafter CPP) should be used with extreme care. For one thing, the CPP doesn’t know about the language it is applied on, it merely proceeds to the translation of the input using very simple rules, and this can leads to tons of hard to detect—and to fix—problems.
In C and C++, the behavior of integer promotions is not the same whether we use signed integers or unsigned integers. In bit twiddling hacks, it is not immediately apparent that it is a problem that may lead to unexpected result whenever code is ported to a different architecture. This is a recurring topic whenever I discuss portability with friends. Very often, they argue that if it works on Windows and 32 bits x86 Linux, that’s pretty much all there is to it.
Of course, I couldn’t disagree more. I have learned the hard way.