On 12/27/2009 7:01 PM, anony wrote:
Eric Niebler pravi:
On 12/27/2009 4:33 PM, anony wrote:
I have this variable definition:
float vertices[][3] = { {-1, -1, 1}, {1, -1, 1}, {1, 1, 1}, {-1, 1, 1}, {-1, -1, -1}, {1, -1, -1}, {1, 1, -1}, {-1, 1, -1} };
I want to scale all elements of vertices, by some constant, for now I do it like this:
BOOST_FOREACH(float& f, boost::make_iterator_range( boost::begin(vertices[0]), boost::end(vertices[7])))
Yikes! You can't do that. The begin and end iterators point into different arrays.
{ f *= scale; }
But maybe something more beautiful could be done with Boost.Range?
Are you certain I am wrong? The array is multidimensional and contiguous in memory. The boost::begin() and boost::end() just return pointers. I have checked if all the floats scale correctly and they do.
I'm pretty certain. You're straying into undefined behavior by making a range using iterators from different arrays.
Why not just use BOOST_FOREACH correctly?
BOOST_FOREACH(float (&rgf)[3], vertices) BOOST_FOREACH(float& f, rgf) f *= scale;
Double loop, oops. Not fancy enough.
Are you joking? -- Eric Niebler BoostPro Computing http://www.boostpro.com