id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
4034	better vector/matrix assignment (or initialization)	Gunter	Gunter	"proposal from Nasos Iliopoulos:

I suppose many of you miss the functionality of creating certain matrices or vectors as in plain c:

double vec[] = {0.1, 2.0, 5.0. 0.3}

With the proposed classes (in the attached file) it is possible to fill vectors and matrices like that:
{{{
vector<double> vec(3);
vec << 1.0, 2.0, 3.0;
}}}
{{{
vector_range<vector<double> > vr (a, range (1, 3));
vr << 11.0, 12.0;
}}}
{{{
matrix<double> mat(3,3);
mat << 1.0, 2.0, 3.0,
       4.0, 5.0, 6.0,
       7.0, 8.0, 9.0;
}}}
or even:
{{{
mat << 1.0, 2.0, 3.0,
       vec,
       7.0, 8.0, 9.0;
}}}
you can also use this form:
{{{
vector<double> vec(10);
vec << 1.0 , project(a, range(0,2)), 10.0, 11.0, a, 15.0, 16.0;
}}}

Another nice trick that is especially useful for sparse matrices and vectors is:
{{{
compressed_matrix<double> cm(3,4, 3*4);
 cm <<  non_vector(4),
        1.0, 2.0, project(a,range(0,2)),
        non_vector(3),2;
}}}
where the non_vector free functions returns a ""non vector"" object that is used to traverse the expression without modifying it.


I would appreciate your general feedback, thoughts, critisism as well as your opinion in the following issues:

- Are there any features beside those presented above and in the attached example that you probably would like to see?
[[BR]]
- Where do you think this should be added? As a separate header file, or included in vector_ and matrix_ expression headers?
[[BR]]
- I found it incovenient to implement this functionallity using iterators (especially when the functions work on sparse types). Does anybody think there are considerable gains if attempting that?
[[BR]]
- I also consider implementing functionality so that project(a, range(..)) << ...; is possible, but I initially faced some problems. I think that _range and _slice classes need to include an operator<< in order for this to work. If somebody wants to work on that it would be great.
[[BR]]
I will write the unit tests if the maintainers consider the proposed code for addition into uBlas.
"	Patches	closed	Boost 1.44.0	uBLAS	Boost 1.42.0	Optimization	fixed	assigment	David Bellot