Re: [boost] Re: ublas: assigning complex to real matrix

From: Toon Knapen (toon.knapen_at_[hidden])
Date: 2002-02-12 06:39:30

jhrwalter wrote:

> --- In boost_at_y..., Toon Knapen <toon.knapen_at_s...> wrote:
> 
>>Currently, real matrices can be assigned to complex matrices due to 
>>
> the 
> 
>>automatic conversion from double to complex. The other direction 
>>
> however 
> 
>>is not supported. To make following code work :
>>
>>numerics::matrix< std::complex< double > > complex_matrix(8,3);
>>numerics::matrix< double > double_matrix(8,3);
>>double_matrix[0] = complex_matrix[0] ;
>>
> 
> Couldn't this be done with 
>  
> double_matrix[0] = complex_matrix[0].real() ;
>  
> or
>  
> double_matrix[0] = numerics::detail::real(complex_matrix[0]) ;
>  
> already?

Is real() a member-function of matrix_row ? or is there a free function 
real() that takes a matrix_row as an argument ? I can't find it. What's 
even more, apparently the square bracket operator on a matrix are 
apparantly not supported anymore. On my latest checkout following does 
not work anymore

vector< double > vector( 3 );
matrix< double > matrix(8,3);
matrix[0] = vector;

>>I patched following files (2 patches follow):
>>
> 
> [Patch snipped]
>  
> Based on our earlier discussion 
> (http://groups.yahoo.com/group/boost/message/21527) we've recently 
> added expression templates for real(vector/matrix) and imag
> (vector/matrix). You'll find the changes in boost CVS. If I've 
> understood your problem correctly, this should help also.
> 

Great if you had added the functionality already. Can you provide a 
small example to show me how to use it ?

> 
>>I also noticed the use of the iterating_assign in vector_assign. 
>>
> Would 
> 
>>you also consider a specialisation to use a memcpy when the 
>>
> value_types 
> 
>>are equal and POD types ?
>>
>  
> This only would work if the rhs in vector_assign would be simple 
> (i.e. another vector). But such an assignment should be handled by 
> the corresponding assignment operator in the the vector class 
> already. IMO the first place to use memcpy as an optimization would 
> be in storage.h for example.
>  
> Regards
>  
> Joerg
> 
> 
> 
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