On 6/8/06, Andy Little <andy@servocomm.freeserve.co.uk> wrote:
Hi Michael,
-----Original Message----- From: Michael Fawcett [mailto:michael.fawcett@gmail.com] Sent: 08 June 2006 15:49 To: andy@servocomm.freeserve.co.uk Subject: Re: [boost] [Review][PQS] Review deadline
A goal of pqs is to be useable in that sort of situation. To be really effective it will need a lot of supporting classes ( matrix, vector, quat) though.
Did you plan on using Boost::uBLAS for this, along with Boost::quaternion? This seemed tangential enough to the PQS discussions that I didn't want to clutter up the mailing list, but I am defeinitely curious.
FWIW Its extremely important. I think it would be worth asking on the list. I dont think many people realise! I have discussed it in various replies but no one has asked me the direct question:
Neither of those libraries above will work with other than numeric types AFAIK. IOW where T is a type (simplifying and ignoring e.g floating point promotion etc), it must satisfy:
T result = T() + T(); T result = T() * T();
(among others)
If T is a physical quantity, the second requirement never can be true. Quantity Compatible library must be written something like:
Where Op is +,-,*,/, ==, etc ...
typeof( T1() Op T1() ) result = T1() Op T2();
This was a private e-mail discussion but Andy thought it important to be bruoght up on the list. FWIW, my own current matrix/vector/quaternion code does what you are asking for (with boost's help), but I had been looking at changing all my stuff over to uBLAS/quaternion for some time. As an example: blas::vec3<float> a(1, 0, 0); blas::vec3<double> b(0, 1, 0); blas::vec3<double> result = cross_product(a, b); // returns vec3<double>! I accomplished this using what I think never became a boost library (from the sandbox maybe? Did MPL::transform consume this functionality?) result_of which was used something like: template <typename LHS, typename RHS> typename boost::result_of_plus<LHS, RHS>::type operator +(const LHS &lhs, const RHS &rhs) { typename boost::result_of_plus<LHS, RHS>::type nrv(lhs); nrv += rhs; return nrv; } I would hope some solution could be found where you didn't have to implement all new matrix/vector/quaternion classes and their corresponding functionality, rather, just ensure the return type from the operation follows normal promotion rules (this is actually what I thought the promotion traits library was going to do). --Michael Fawcett