Re: [boost] [random] Minor problem with lognormal_distribution

From: David Abrahams (dave_at_[hidden])
Date: 2003-02-25 07:44:11

Michael Stevens <Michael.Stevens_at_[hidden]> writes:

> Dear Boosters,
>
> This is just a quick reminder of regression before boost_1_30_0 gets
> released. Without CVS access I can fix it myself and Jens seems to be
> offline at the moment. It would be great if someone could step in and
> make a simple correction.
>
> The regression is the the return values of the mean and sigma values
> of boost::random::lognormal_distribution.
>
>
> Correction required for boost/random/lognormal_distribution. hpp line 67-68
>
> RealType& mean() const { return _mean; }
> RealType& sigma() const { return _sigma; }
>
> should read.
>
> RealType mean() const { return _mean; }
> RealType sigma() const { return _sigma; }
>
>
> The correction makes the return values identical with those of other
> real distributions, cf. normal_distribution line 62
>
> The problem can simply be tested by instantiating the template thus
> template boost::normal_distribution<boost::mt19937, float>;
>
> It should be noted that the problem is NOT picked up by regression
> tests in random_test.cpp. The current test procedure
> void instantiate_dist(const char * name, const Dist& dist)
> uses a reference to a constant distribution. It therefore fails to
> pickup on the return of non constant member reference.

Michael,

Could you please suggest a patch for the regression tests which will
detect this problem?  It's always better to get the test to fail
first before we check in any fixes.

Thanks,
Dave

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com