Re: [boost] [fusion] matrix?

From: Andy Little (andy_at_[hidden])
Date: 2006-09-09 18:54:36

"Andy Little" <andy_at_[hidden]> wrote in message
news:edv632$3ku$1_at_sea.gmane.org...
>
> "Joel de Guzman" <joel_at_[hidden]> wrote in message
> news:edu4v2$beb$1_at_sea.gmane.org...
>> Andy Little wrote:
>
>>> BTW. By using a tuple rather than an array, then you can  use representing
>>> zero
>>> and one. IOW zero<T> one<T> .
>>>
>>> hence:
>>>
>>> template <typename TL, typename TR>
>>> zero<typeof(TL() * TR() )>
>>> operator *( Tl , zero<TR>)
>>> {
>>>     return zero<typeof(TL() * TR() )>();
>>> }
>>> It should be relatively simple for the compiler to optimise such calcs away.
>>> Very useful for matrix calcs.
>>> (originally suggested by Geoffrey Irving).
>>
>> Indeed. Also, with Fusion, you have the option to use purely
>> constant sequences such as mpl::vector_c together with plain
>> sequences, or even user defined sequences and adapted/converted
>> structs/classes.
>
> Right. I started looking into this scheme for math ops. I opted for a zero and
> a
> one, but then I figured that one + one should go to two etc.
>
> In the end I opted for  a static_value<StaticValue,RunTimeType>
>
> StaticValue could then  be any of mpl::int_ etc, though for mpl int_ division
> is
> ( can be) lossy so at that point the division should turn the result into the
> RunTimeType. other possibilities for StaticValue are a compile time rational,
> maybe with a long long value_type. At any point where the compile time value
> will run out of steam then the type will be automatically converted to the
> RunTimeType.
>
> All in all... how to take a simple idea and make it very very complicated :-)

Oh Yeah, and plug in variadic templates, auto, and stick the kettle on while
waiting for it to compile and you will probably not spend as much time worrying
about sparse matrices. ;-)

regards
Andy Little