Well due to the fact that floats are represented on 4 bytes, there shouldn't be any padding involved. Padding normally occures when certain member variables of a structure require certain alignment constraints or just for efficiency, but this shouldn't occur with a vector class (at least that is my understanding). It is the same thing with alignment. the beginning of the structure is placed on a certain boundary but doesn't affect the padding of elements within the structure. You could set this vector class to be 16 bytes aligned if you wanted to use them with SSE instructions, and you can still access the member with the array operator without problems. Olivier. On 9/22/06, Sohail Somani <s.somani@fincad.com> wrote:
Won't that not work in the presence of padding? Sorry for the TP, lookout webmail.
-----Original Message----- From: boost-bounces@lists.boost.org on behalf of Marcus Lindblom Sent: Fri 9/22/2006 12:17 AM To: boost@lists.boost.org Subject: Re: [boost] Geometry/Vector Lib
Olivier Grant wrote:
I agree on your point, on the other hand, you can do this :
class vector3d { public: float x, y, z;
float operator[]( int index ) const { return ((float *)this)[index]; }
float & operator[]( int index ) { return ((float *)this)[index]; }
/* ... */ };
in which case "v.x" and "v[0]" are the same thing. this is what I currently have. Now some people will argument its a hack maybe.
I've sometimes done just:
class vector3d { public: float x, y, z;
float operator[]( int index ) const { return (&x)[index]; }
/* ... */ };
/Marcus _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost