iterator problem in ublas::basic_range (boost/numeric/ublas/storage.hpp)

[brian.tyler@…]

Decrementing (--) a forward iterator through a basic_range containing negative values throws an error (bad_index). This seems inconsistent because it is possible to increment (++) through such a range without throwing error.

lines 937 - 941 of boost/numeric/ublas/storage.hpp read

const_iterator &operator -- () {
  BOOST_UBLAS_CHECK (it_ > 0, bad_index ());
  -- it_;
  return *this;
}

Removing "BOOST_UBLAS_CHECK (it_ > 0, bad_index ());" solves the problem. Similarly for the += and -= operators.

The documentation makes no mention of the range needing to consist only of positive values and this seems a rather arbitrary restriction.

[Gunter]

The type of indices is by default "unsigned long". Thus we have to assure that we do not decrement a 0. Support of signed types for indices requires some work - I'll change this task to a feature request.

Additionally, we should add checks to the increment functions.