On Tuesday 08 July 2003 08:01 am, Neal D. Becker wrote:
> On Monday 07 July 2003 05:06 pm, Jens Maurer wrote:
> > I've updated the current Boost.Random CVS to the interface
> > contained in the C++ library TR proposal:
> >
> > http://std.dkuug.dk/jtc1/sc22/wg21/docs/papers/2003/n1452.html
> >
> > The boost documentation has not yet been updated, I hope to be able
> > to do that later this week. Reading the TR proposal should give
> > you a sufficient idea.
> >
> > There have been various suggestions for changes from C++
> > committee members, so additional (but minor) interface changes
> > may happen after the October 2003 meeting.
>
> I would also like to suggest one addition that is very useful. It is very
> common in communications to need a generator that produces a 1-bit
> sequence.
After some reflection, I think a somewhat more generalized version might be
even better. This one can produce sequences of n-bit rather than only 1-bit.
I'm not sure what to do with max_value and min_value. It depends on
interpretation- whether you intend to sign extend the values and interpret
them as signed or zero extend and interpret as unsigned.
#ifndef pnseq_generator_H
#define pnseq_generator_H
#include <boost/random.hpp>
namespace boost
{
namespace random
{
template < class RandomNumberGenerator, int width=1 >
class pnseq_generator
{
public:
typedef pnseq_generator<RandomNumberGenerator> self_type;
typedef RandomNumberGenerator base_type;
typedef int result_type;
BOOST_STATIC_CONSTANT (bool, has_fixed_range = true);
BOOST_STATIC_CONSTANT (result_type, min_value = 0);
BOOST_STATIC_CONSTANT (unsigned int, max_value = ~(unsigned(-1) <<
width));
BOOST_STATIC_CONSTANT (int, mask = ~(unsigned(-1) << width));
result_type min() const
{ return min_value; }
result_type max() const
{ return max_value; }
explicit pnseq_generator (base_type & rng)
: rng_( rng ), count_()
{ init(); }
template < typename T >
void seed( T s )
{ rng_.seed( s ); init(); }
result_type operator()()
{
int const bits = cache_ & mask;
cache_ >>= width;
if ( --count_ <= width-1 )
init();
return bits;
}
bool validation( result_type x ) const
{ return valid == x; }
friend bool operator ==( self_type const &x, self_type const &y )
{
return x.rng_ == y.rng_ && x.cache_ == y.cache_
&& x.count_ == y.count_;
}
friend bool operator !=( self_type const &x, self_type const &y )
{ return !(x == y); }
private:
typedef typename base_type::result_type cache_type;
void init()
{
cache_ = rng_();
count_ = std::numeric_limits<cache_type>::digits;
}
base_type& rng_;
cache_type cache_;
int count_;
}; // boost::random::pnseq_generator
} // random
} // boost
#endif
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