id,summary,reporter,owner,description,type,status,milestone,component,version,severity,resolution,keywords,cc
920,Proposed extension to random library,nobody,jmaurer,"{{{
I suggest adding the following utility function to
the random library (with perhaps a name change):

// PURPOSE: Sample from a set of N values given the
// sequence p[1], p[1] + p[2], p[1] + p[2] + p[3], ...
// of cumulative probabilities.
//
// REQUIRE:
// - Type Incrementer supports the pre-increment
//   operation and equality comparison.  Typically,
//   Incrementer will be an integral type or a
//   forward iterator.
// - Pre-incrementing i some finite number of times
//   -- say, N -- makes it equal to iend.
// - cumprob_it ""points"" at a nondecreasing sequence
//   of at least N nonnegative numbers, with the N-th
//   value in the sequence being equal to 1.0.
//
// RETURNS:
// A random value in the interval [i, iend), with
// cumprob_it defining the sequence of cumulative
// probabilities.

template <typename InputIterator,
          typename Incrementer,
          class UniformRandomNumberGenerator>
Incrementer
rand(Incrementer i, Incrementer iend,
     InputIterator cumprob_it,
     UniformRandomNumberGenerator & rng)
{
  typedef
    std::iterator_traits<InputIterator>::value_type
    number_t;
  uniform_01<UniformRandomNumberGenerator, number_t>
    urng(rng);
  number_t p = urng();
  for ( ; p >= *cumprob_it; ++cumprob_t) {
    ++i;
    assert(!(i == iend));
  }
  return i;
}

-- Kevin S. Van Horn (Kevin_VanHorn@ndsu.nodak.edu)
}}}",Feature Requests,closed,,random,None,Problem,fixed,,