Re: [boost] [random] geometric_distribution backwards compatibility

Subject: Re: [boost] [random] geometric_distribution backwards compatibility
From: Patrick Horgan (phorgan1_at_[hidden])
Date: 2011-01-24 01:26:24

On 01/23/2011 04:40 PM, Steven Watanabe wrote:
> AMDG
>
>   Over the last year I've been (slowly) updating
> Boost.Random to match the new standard.  Unfortunately
> I just hit a problem that I don't have a good solution
> for.  In the standard, the geometric_distribution is
> defined as $p(i) = p(1-p)^{i}$, with i >= 0.  In the
> current Boost.Random code it is $p(i) = (1-p) p^{i-1}$,
> with i >= 1.  The definition in the standard makes
> more sense, but I don't want to introduce a breaking
> change.  I can see two options here:
>
> * Leave the implementation alone and put a big
>   warning in the documentation saying that the
>   behavior doesn't match the standard.

That's not good.  Why would anyone want to use it after the 
documentation said that?

> * Since I'm also moving things into namespace
>   boost::random, I can use the new definition
>   and leave a version with the old behavior in
>   namespace boost instead of having a using
>   declaration.  I'd still have to add a warning
>   that boost::geometric_distribution isn't the
>   same as boost::random::geometric_distribution.

That's better than the other, but I'd like to hear about the downside of 
a breaking change.

Patrick