[boost] Re: N-arity operators in C++, also reducing temporaries. [Repost]

From: Pavel Chikulaev (pavel.chikulaev_at_[hidden])
Date: 2005-03-08 05:52:00

"Tobias Schwinger" <tschwinger_at_[hidden]> wrote in message 
news:d0igjh$46u$1_at_sea.gmane.org...
> - Custom per element operations
    You mean
        matrix<double> m;
        double d = transpose(m)[5][6]; //
    don't you?
    It's not yet supported, but I think I can do it.

    Thanks.

> - It should not be limited to operators but work with any functions

N-Arity Functions are already supported. It is so called custom operations.
Transpose function is example from sample usage.
Another example:

class product_t;

same class Matrix
{
    //..
    Matrix(LAZY_CUSTOM_OP(product_tag, (2, (Matrix_, Matrix_)));
    LAZY_ENABLE_CUSTOM_OP(product, Matrix_ = 
lazy::custom_op<product_tag>((Matrix_, Matrix_)));
};

Matrix::Matrix(LAZY_CUSTOM_OP(product_tag, (2, (Matrix_, Matrix_)) op)
{
    //first matrix accessed via op._1
    //second matrix accessed via op._2
}

//..
Matrix a, b, c;
//..
a = product(b, c); //No temporaries

The only drawback of such approach is that I can't add a lazy function 
without
changing class. But I'm working on it. I think it's not necessary to change 
class
definition.

Eurika! I know how to do it.
Template specialiation will help me again.

Thanks again!

> The design should allow to optionally replace operations to make use of 
> SIMD hardware.

Library also supports it. AFAIK It's template specialization of lazy
operator, isn't it?

--
Pavel Chikulaev