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Re^3: Can you spot the problem?

by adrianh (Chancellor)
on Mar 05, 2004 at 14:41 UTC ( #334225=note: print w/replies, xml ) Need Help??

in reply to Re: Re: Can you spot the problem?
in thread Can you spot the problem?

instead it does something that doesn't even make sense

I disagree. Most people would expect a bitwise-or of a series of numbers. In many languages it would do exactly what the author intended.

...but we're moving hint territory :-)

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Re: Re^3: Can you spot the problem?
by flyingmoose (Priest) on Mar 05, 2004 at 15:30 UTC
    Yes, and even trying for a bitwise-or (which this is not) in this particular example is bad design. The explicit if-test as little proposed is what you want.

    C programmers are well known to do a x|=0x0000FFF << 7 + 3 and other wacky stuff when simpler things work. Also bad form. Yes, I'm giving the meta-response, deal with it :)

      I could agree with "bad design" (I probably wouldn't in this particular instance - but it's certainly an arguable point).

      However "something that doesn't even make sense" is a somewhat stronger statement than "bad design" :-)

      The line makes complete sense as a numerical bitwise or, and the reason it does not do what the author expects is non-obvious in my opinion.

        However "something that doesn't even make sense" is a somewhat stronger statement than "bad design"

        In some respects, I agree with the statement that the original code as posted doesn't make sense. It "feels" to me like something that would be posted as Obfuscated Code, because instead of going about solving the problem in any normal way, it attempts to abuse certain lowlevel features of the dataset in order to achieve a counterintuitive solution.

        Normally, one would not expect to be able to compare four numbers with a fifth number by bitwise or-ing the four numbers together and comparing the result to the fifth number. In the general case, this would not work. It took me three readings of the code to understand why the author *expected* it to work. Of course, it doesn't, because he ignored something else that is comparably low-level in nature to the thing he was exploiting.

        The code is attempting (and failing) to take advantage of some lowlevel details not only of how the language works but also lowlevel details of the dataset and of the problem. If 256 weren't a power of two, there wouldn't even be a presumption that it might work. It's a lowlevel bit-fiddling dirty-trick (attempted) solution to a higher-level problem, by no means a natural way to go about the thing at hand. Notice I did not say it isn't *the* natural way; I said it is not *a* natural way at all. Id est, it doesn't make sense.

        People who write code like this *deserve* to get bitten by lowlevel details. (Of course, if you're just fooling around and the results don't matter, then getting bitten isn't such a big deal.)

        ;$;=sub{$/};@;=map{my($a,$b)=($_,$;);$;=sub{$a.$b->()}} split//,".rekcah lreP rehtona tsuJ";$\=$;[-1]->();print

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