Re: [Boost-users] [Random] Passing an arbitrary uniform random number generator to a function

Your mention of "you need type erasure" makes me think of using boost::function to do the job, which I suppose could replace the explicit writing of the runtime_generator class. But still, nice idea to wrap the virtual function taking the wrapped thing with a non-virtual template member that does the wrapping.

-----Original Message----- From: boost-users-bounces@lists.boost.org [mailto:boost-users- bounces@lists.boost.org] On Behalf Of Joseph Gauterin Sent: Tuesday, April 27, 2010 6:50 AM To: boost-users@lists.boost.org Subject: Re: [Boost-users] [Random] Passing an arbitrary uniform random number generator to a function

Looks like you need some sort of type erasure (Steve's suggestion uses boost::function for that):

* Create a class that can be passed to uniform_real as a generator - that is what Steve's runtime_generator class is for. * Give runtime_generator a constructor that takes a single argument of a template type, initialize min_ and max_ from that and store the argument in impl (that will compile if the argument is a rng that follows the correct conventions) * Write the virtual function you wanted taking an argument of type runtime_generator<double>& - but make it private * Write a non-virtual public template function to wrap the rng

It's difficult to explain concisely - here's what the code should look like (untested - just for explanation):

template<class ResultType> class runtime_generator { public:

template <class T> explicit runtime_generator(T& rng) : min_(rng.min()), max_(rng.max()), impl(rng) { }

ResultType min() const { return min_; } ResultType max() const { return max_; } ResultType operator()() { return impl(); }

private: ResultType min_, max_; boost::function impl; };

//in your class... public: template<class rng_t> double foo(rng_t& urng) { runtime_generator<double> rtRNG(urng); return foo_(rtRNG); }

private: virtual double foo_(runtime_generator<double> &urng) { double x = uniform_real<double> (0.0, 10.0) (urng); double y = uniform_real<double> (5.0, 7.0) (urng); return (x*y); } _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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