From help-request at octave dot org Sun Jan 23 21:26:41 2005
Subject: mkoctfile questions
From: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
To: Brian Blais <bblais at bryant dot edu>
Cc: help at octave dot org
Date: Sun, 23 Jan 2005 22:30:17 -0500

On 23-Jan-2005, Brian Blais <bblais at bryant dot edu> wrote:

| I have a few questions about making dynamically linked functions, and
| the libOctave.
| 
| 1) are the any example files for doing simple things with the Matrix
| class?  There is the Octave dynamically linked cookbook, which I find
| very useful, but is there anything else?  a directory with some toy
| examples would be the easiest to make, and for me the most useful.

The Octave sources themselves provide a number of examples.

| 2) how do you extract elements from a multi-dimensional matrix?

The best method depends on precisely what you want to do.

| 3) how do you work with uint8 matrices?

Take a look at ov.h.  You can do things like:

  uint8NDArray x = val.uint8NDArray_value ();

Elements of x are of type octave_uint8.

| is there a way to tell whether a matrix passed into a dld is uint8?

Not currently.  It is generally better to use something like

  uint8NDArray x = val.uint8NDArray_value ();

  if (! error_state)
    {
      // Do something with x.
    }
  else
    // Handle error.

instead of

  if (val.is_the_type_i_want ())
    {
      // extract value, etc.
    }

because then you can take advanage of any automatic type conversions
that may exist.

If you really need functions like is_uint8_scalar(),
is_uint8_matrix(), etc., then perhaps the best way to get them into
Octave is to write the code and submit a patch.

jwe



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