I was playing around with Boost.Array tonight, seeing if I could make the signatures more closely match std::array. Specifically, I wanted to add 'constexpr' to "operator [] (size_t) const" and "at (size_t) const"as proposed in http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3470.html But I ran into a problem. Here are the implementations: const_reference operator[](size_type i) const { BOOST_ASSERT_MSG( i < N, "out of range" ); return elems[i]; } const_reference at(size_type i) const { rangecheck(i); return elems[i]; } static void rangecheck (size_type i) { if (i >= size()) { std::out_of_range e("array<>: index out of range"); boost::throw_exception(e); } } BOOST_ASSERT does not fit into the constexpr world at all, and neither does rangecheck. I could rewrite rangecheck so it could be constexpr, but only (I believe) by throwing the exception directly, rather than using boost::throw_exception. static void rangecheck (size_type i) { if (i >= size()) throw std::out_of_range e("array<>: index out of range"); } or even just: BOOST_CONSTEXPR const_reference at(size_type i) const { return i >= size () ? throw std::out_of_range e("array<>: index out of range") : elems[i]; } Has anyone put any effort into making Boost.Exception (and BOOST_ASSERT) work with constexpr? -- Marshall Marshall Clow Idio Software <mailto:mclow.lists@gmail.com> A.D. 1517: Martin Luther nails his 95 Theses to the church door and is promptly moderated down to (-1, Flamebait). -- Yu Suzuki