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Re: new types and INSTALL_BINOP

From: John W. Eaton
Subject: Re: new types and INSTALL_BINOP
Date: Thu, 1 Mar 2001 20:28:00 -0600

On  1-Mar-2001, address@hidden <address@hidden> wrote:

| Great, that makes a lot of sense for my case, because this
| is the best way to handle most operators.
| For example:
|    sparse_matrix + 1
| is best handled by converting it to a "full" matrix   
| Unfortunately, I don't understand the details of how to make
| this work.
| I have conversion methods for this, eg:
|    Matrix octave_sparse::matrix_value (bool = false) const {
|       Matrix M= oct_sparse_to_full( X );
|       return M;
|    }

(I'd write the body of this function as just

  return oct_sparse_to_full (X);

since there is no need to have the declaration/initialization
statement here.)

| How do I register this with do_binary_op so that it can
| call my function?

Here is how it is done for the bool_matrix class.  In ov-bool-mat.h:

  octave_bool_matrix : public octave_base_matrix<boolMatrix>
    type_conv_fcn numeric_conversion_function (void) const;

and in

  static octave_value *
  default_numeric_conversion_function (const octave_value& a)
    CAST_CONV_ARG (const octave_bool_matrix&);

    return new octave_matrix (Matrix (v.bool_matrix_value ()));

  octave_bool_matrix::numeric_conversion_function (void) const
    return default_numeric_conversion_function;

Your conversion function would be

  static octave_value *
  default_numeric_conversion_function (const octave_value& a)
    CAST_CONV_ARG (const octave_sparse&);

    return new octave_matrix (v.matrix_value ());

(I should probably define an octave_bool_matrix::matrix_value member

The reason for having the function that returns the address of the
conversion function is to avoid headaches with pointers to member
functions and at the same time keep the conversion function out of the
global namespace.


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