Next: Operator Overloading, Up: Overloading Objects [Contents][Index]
Any Octave function can be overloaded, and this allows an object-specific
version of a function to be called as needed. A pertinent example for the
polynomial class might be to overload the polyval
function.
function [y, dy] = polyval (p, varargin) if (nargout > 1) [y, dy] = polyval (fliplr (p.poly), varargin{:}); else y = polyval (fliplr (p.poly), varargin{:}); endif endfunction
This function just hands off the work to the normal Octave polyval
function. Another interesting example of an overloaded function for the
polynomial class is the plot
function.
function h = plot (p, varargin) n = 128; rmax = max (abs (roots (p.poly))); x = [0 : (n - 1)] / (n - 1) * 2.2 * rmax - 1.1 * rmax; if (nargout > 0) h = plot (x, polyval (p, x), varargin{:}); else plot (x, polyval (p, x), varargin{:}); endif endfunction
which allows polynomials to be plotted in the domain near the region of the roots of the polynomial.
Functions that are of particular interest for overloading are the class
conversion functions such as double
. Overloading these functions allows
the cast
function to work with a user class. It can also aid in the
use of a class object with methods and functions from other classes since the
object can be transformed to the requisite input form for the new function.
An example double
function for the polynomial class might look like
function a = double (p) a = p.poly; endfunction