Re: basic DLD help?

[Paul Kienzle]

Octave doesn't allow in-place modification of arrays.  Instead you need 
to make a copy and return it.

Use:

    octave_value_list retval;
        RowVector y(args(0).vector_value());
        double *py = y.fortran_vec();
    ...
    retval(0) = y;
    return retval;

- Paul

On Jul 14, 2005, at 6:22 AM, Shai Ayal wrote:

> Ah,
>
> but what if I do want to change the data ?
>
> Shai
>
> John W. Eaton wrote:
> > On 13-Jul-2005, David Bateman wrote:
> > | Even better would be
> > | |    const RowVector y(args(0).vector_value());
> > |    const double *py = y.fortran_vec();
> > | | since as you say fortran_vec calls make_unique except when 
> > "const", and | since you aren't altering the data past to the 
> > function, in this manner | you avoid a copy.
> > Still better would be
> >   const RowVector y(args(0).vector_value());
> >   const double *py = y.data();
> > because if you are only asking for read-only access, you can use the
> > const data() method and avoid the call to make_unique().
> > As I recall, the reason for having different names (fortran_vec and
> > data) was because it was not possible to overload on const in early
> > C++ dialects.  Now that it is possible, I suppose we could use just
> > one name instead of two.
> > jwe



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