Re: [boost] Formal review request: static size matrix/vector linear algebra library (Boost) LA

Subject: Re: [boost] Formal review request: static size matrix/vector linear algebra library (Boost) LA
From: Agustín K-ballo Bergé (kaballo86_at_[hidden])
Date: 2010-02-10 19:37:42

El 09/02/2010 03:45 a.m., Emil Dotchevski escribió:
> 2010/2/8 Agustín K-ballo Bergé <kaballo86_at_[hidden]>:
>> boost::la::la_detail::vref_< T > get( int index )
>> {
>>    return boost::la::vref( ... );
>> }
> 
> I was actually interested in the ... part :)

It's merely an expression that returns a T(&)[N].

> Why isn't it plausible for you to do:
> 
> my_own_conforming_vector_type get( int index )

I want to return a conforming vector type, and whatever vref returns
fills the bill perfectly. My project is a generic OpenGL model,
specialized by a sequence of attributes that describe a vertex.

>> In my current project I use the library to generically work with any
>> conforming vertex type, so I can't use the subscript operator since it
>> would be optional. That's why I propose adding support for subscript
>> operator via vref/mref. vref/mref would wrap the UDTs and implement the
>> subscript operators, similar to what they currently do for arrays.
> 
> However, all this presumes that op| doesn't work well. The only
> potential issue with it is the low precedence. Is that why you'd
> rather use op[ ]?

I have been bitten by the precedence issue to the point I enclose every
pipe operation in parenthesis. And it gets worse if "complex swizzling
expressions" are added to the library. Consider

( v1 | ( Y, -X ) ) * 2;

versus

v1[ Y, -X ] * 2;

It *might* be possible to get ride of the precedence problems by using
expression templates, but even then subscripting operator seems more
natural.

K-ballo.-
http://talesofcpp.blogspot.com