Re: [boost] [fusion] matrix?

From: Andy Little (andy_at_[hidden])
Date: 2006-09-17 10:16:45

"Larry Evans" <cppljevans_at_[hidden]> wrote in message 
news:eejch5$a8t$1_at_sea.gmane.org...
> On 09/05/2006 08:36 AM, David Abrahams wrote:
>> "Andy Little" <andy_at_[hidden]> writes:
>>>Is it possible to use fusion to do a compile time matrix?
>>
>> Not directly, but there are at least two good ways to build one on top
>> of fusion:
>>
>> 1. use a fusion vector of fusion vectors.
>> 2. use a fusion vector augmented with a row length (assuming it's row-major).
>>
> Andy,
>
> It suddenly dawned on me that 1 above seems a pretty simple solution.
> Is there some reason for not using 1?

Well, Lets assume that you could use one infinitely long sequence. That is 
slightly simpler  (IMO) because it would work exactly the same for any size 
matrix, iow each could have the same representation, which might be something 
like:

matrix<rows, columns, sequence>

which actually is what I am currently going for.

 I havent tried the alternative., but I suspect that the metaprogramming of it 
would be more complicated.

Ultimately I suppose the interface should be separated from the implementation 
and it should work for both, however I'm certainly not planning something 
suitable for a boost review, just something where I can say 'look ma, it works!" 
if you get my drift :-), but in fact to get a row or a column you will probably 
need a fusion::View either way at some stage.

If I can get to be able to produce a cofactor matrix and the inverse then I 
reckon I will have succeeded.; -)

BTW, if you look at my inner_product.zip example in the Generic Programming 
section of the vault you will see why it is advantageous to be able to have 
arbitrary elements, even if they are just meant to stand in for doubles.

Also BTW my other aim is following the book I bought called "Quaternions and 
Rotation sequences A primer with Applications to Orbits Aerospace and Virtual 
Reality", by Jack B. Kuipers. That might give a clue that my understanding of 
the subject isnt that advanced ;-)

 The ultimate aim being to make some sort of virtual reality using my Quan 
library. That's the dream anyway :-)

regards
Andy Little