Re: [Boost-users] Boost.Range fancify please

Subject: Re: [Boost-users] Boost.Range fancify please
From: anony (janezz55_at_[hidden])
Date: 2009-12-27 01:01:56

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.

> 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.