Getting arguments in oct-files - per reference or not?

[Daniel Kraft]

Hi all!

To extract arguments in an oct-file, I frequently do things like this:

    const boolNDArray inside = args(3).bool_array_value ();
    const Matrix bdryCoords = args(4).matrix_value ();
    const ColumnVector intsecIn = args(5).column_vector_value ();

The matrices / arrays / vectors involved can be quite large.  Now, I
discovered that it also works if I store only a *reference*, i. e.,

    const boolNDArray& inside = args(3).bool_array_value ();
    const Matrix& bdryCoords = args(4).matrix_value ();
    const ColumnVector& intsecIn = args(5).column_vector_value ();

Presumably, the second form is more efficient, since it avoids an
unnecessary copy.  However, I'm unsure if it is actually correct -- this
depends on how the octave_value does things internally.

Is it save to store the result of octave_value::matrix_value() (and
friends) in a reference, as long as the octave_value doesn't go out of
scope?  Or will this be a reference to some temporary object that is not
guaranteed to persist the matrix_value() call?

Thanks!  Yours,
Daniel

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