Review Request: Convenience KRandom methods

[Ingo Klöcker]

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trunk/KDE/kdelibs/kdecore/util/krandom.h
<http://reviewboard.kde.org/r/4992/#comment7031>

    This is wrong. Quoting the man page of rand (3):
    "The rand() function returns a pseudo-random integer in the range [0, RAND_MAX]."
    
    Note the closing ']'.



trunk/KDE/kdelibs/kdecore/util/krandom.cpp
<http://reviewboard.kde.org/r/4992/#comment7030>

    This will probably crash if you call it with min = MIN_INT and max = MAX_INT because then max-min+1 = 0 (due to an integer overflow). In fact, even smaller ranges will most likely be problematic as soon as max-min+1 > MAX_INT.
    
    Apart from the integer overflow problem this method will not return uniformly distributed random numbers. See for example http://www.cplusplus.com/reference/clibrary/cstdlib/rand/.
    
    If you want uniformly distributed random numbers in a certain integer range then use
    http://www.boost.org/doc/libs/1_43_0/doc/html/boost_random/tutorial.html#boost_random.tutorial.generating_integers_in_a_range
    instead of trying to re-invent a wheel that is much more complicated than you think.
    
    As far as I'm concerned I'm against adding such a flawed method to kdelibs.


- Ingo


On 2010-08-12 13:40:52, Sebastian Trueg wrote:
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> (Updated 2010-08-12 13:40:52)
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> 
> Review request for kdelibs.
> 
> 
> Summary
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> The KRandom namespace is quite useful. However, applications need to be full of code snippets that calculate a random number in a range. IMHO it makes perfect sense to do this once in the library. Thus, I am proposing this patch to introduce two methods providing random numbers from a range.
> Feel free to improve the implementation. :)
> 
> 
> Diffs
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>   trunk/KDE/kdelibs/kdecore/util/krandom.h 1162164 
>   trunk/KDE/kdelibs/kdecore/util/krandom.cpp 1162164 
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> Diff: http://reviewboard.kde.org/r/4992/diff
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> 
> Testing
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> 
> Thanks,
> 
> Sebastian
> 
>

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