On Feb 24, 7:03 pm, [EMAIL PROTECTED] (Aahz) wrote: > In article <[EMAIL PROTECTED]>, > Jeff Schwab <[EMAIL PROTECTED]> wrote: > >(3) Garbage collection is at least as desirable a language feature as > >deterministic destruction. > > Enh. There probably are some people who claim that, but I can't think > of any off-hand.
I am most certainly claiming it; in fact I'm claiming that GC far more desirable, because the cost of deterministic destruction is too high. The costs are: 1. extra effort (which Jeff Schwab denied but I don't remotely buy it) 2. mistakes are easier to make and more catastrophic when made With deterministic destruction, you have to worry about the lifetime of every single object, and that requires effort. Either you are literally keeping track of all the object and manually freeing and deleting them like in C, or you are sticking to a rigid disciplined style that (mostly) guards against practices that lead to invalid pointers and memory leaks. The discipline itself takes effort, but the rigid style also limits expressiveness, often severely, and so you have to expend more effort writing the same thing. Point is, one way or another, you are paying for deterministic destruction with more effort. Even that innocuous object on the local stack frame can bite you if you pass it to a function that, expecting a heap object, stores a pointer. Which means you have to keep track of what the functions you're calling do, and you have to be deliberate about what the functions you're writing do, so still more effort, yadda yadda. I don't really think I have to say much with regard to error-proneness compared to GC, nor the cost of mistakes Invalid pointer dereferences and segfaults don't happen in Python (aside from extensions), and memory leaks only happen when you accidentally keep objects alive. Mistakes are far more common and dangerous in C++. And subtle I might add. A destroyed object that is improperly derferenced might "work" for awhile since its memory hadn't been overwritten, then suddenly crash and burn in slightly different circumstances (such as if it's running a different computer, like, for instance, the customer's). And tracking down and fixing those bugs, compared to the sorts of bugs you get from garbage collection? You guessed it--more effort. Deterministic destruction would be a great thing if it weren't for all the drawbacks. Until then I will choose the path of lesser effort by letting GC take care of memory, closing my own files, and having lots of expressive power and freedom. Carl Banks -- http://mail.python.org/mailman/listinfo/python-list
