Re: [boost] [qvm] Terseness of syntax etc.

8 Dec 2015

      Phil, thank you for your feedback.

On Tue, Dec 8, 2015 at 8:25 AM, Phil Endecott <
spam_from_boost_dev@chezphil.org> wrote:
...
I find most of the identifiers too short.  To give just a couple
of examples: "transp" is used to mean "transpose".  You save
typing three letters, and get confusion with transparent,
transport, etc.  Then look at the names of some traits classes;
elsewhere we have type_traits, allocator_traits, iterator_traits
etc. all spelt out in full, but in qvm we have q_traits, v_traits
and m_traits.
I agree that transp is perhaps too short. The q_, v_ and m_traits though
shouldn't be a problem since throughout the entire library q, v and m mean
the same thing.
...
I had a quick think about how a struct with x,y,z members could
be adapted.  Am I right in thinking that it would be necessary to
write accessors like this inside the traits specialisation:
float ir(int i, xyz_vec const & v) {
  switch (i) {
    case 0: return v.x;
    case 1: return v.y;
    case 2: return v.z;
  }
}
The ir/iw accessors are for dynamic indexing and are generally optional.
You use r and w for read and write access and in that case access to x, y
and z can be implemented as specializations. I know, short names. :)

So:

struct float3 { float x,y,z; };

namespace
boost
    {
    namespace
    qvm
        {
        template <class V> struct v_traits;
        template <> struct v_traitsre::float3
            {
            typedef float scalar_type;
            static int const dim=3;
            template <int I> static float r( float3 const & );
            template <int I> static float & w( float3 & );
            };

        template <> float v_traitsre::float3::r<0>( float3 const & a ) {
return a.x; }
        template <> float v_traitsre::float3::r<1>( float3 const & a ) {
return a.y; }
        template <> float v_traitsre::float3::r<2>( float3 const & a ) {
return a.z; }

        template <> float & v_traitsre::float3::w<0>( float3 & a ) {
return a.x; }
        template <> float & v_traitsre::float3::w<1>( float3 & a ) {
return a.y; }
        template <> float & v_traitsre::float3::w<2>( float3 & a ) {
return a.z; }
        }
    }

I'm really not a fan of the old operator% and now operator, syntax.
...
To me, (v,XY) looks like you're forming a row-vector with two elements.
Is there a reason why these accessors can't be written with function
syntax, i.e. XY(v) ?  Or, for matrices, something like element<4,2>(m)
rather than (m,A<4,2>) ?
There is (m,A42) actually which seems preferable to element<4,2>(m). There
is no good solution for swizzling, unfortunately. I ended up with comma
because it looks nice to my eye, in combination with the parentheses. I can
list several problems of choosing comma, much like I can for any other
choice. :)

Thanks,
Emil http://www.revergestudios.com/reblog/index.php?n=ReCode

Re: [boost] [qvm] Terseness of syntax etc.

Emil Dotchevski