How to pass a ublas::matrix to a C API

[sanjeev.p3]

I need to pass ublas::matrix data to a legacy C API which expects
input in the form:

void doSomething(double* data,...);

If I have a std::vector<double> myA this is easy. I do:

doSomething(&myA[0],...);

I am not sure what to do with my ublas::matrix<double> myB?

I tried:

matrix_column<matrix<double> > x1(myB, 0); //get a proxy to the
1st column
doSomething(&x1[0],...);

but this results in a "differs in levels of indirection from
'boost::numeric::ublas::matrix_column<M>" error. Is there a way to do
this without copying to another data strucutre before passing?

Thanks,
Sanjeev

 

[carvalho.miguel]

I need to pass ublas::matrix data to a legacy C API which expects
input in the form:

void doSomething(double* data,...);

If I have a std::vector<double> myA this is easy. I do:

doSomething(&myA[0],...);

I am not sure what to do with my ublas::matrix<double> myB?

I tried:

matrix_column<matrix<double> > x1(myB, 0); //get a proxy to the
1st column
doSomething(&x1[0],...);

but this results in a "differs in levels of indirection from
'boost::numeric::ublas::matrix_column<M>" error. Is there a way to do
this without copying to another data strucutre before passing?

Thanks,
Sanjeev

have you tried matrix_row instead?
if it still doesnt work, maybe ublas has an internal design which
doesnt allowed that kind of argument passing, which means you will
have to create a vector (or array for that matter) for each row or
column of the matrix before sending it to the function (using a for
loop).
cant be of better help, since my understanding of ublas is very
limited (aka havent worked much with it).