<html lang="en"> <head> <title>Function Overloading - Untitled</title> <meta http-equiv="Content-Type" content="text/html"> <meta name="description" content="Untitled"> <meta name="generator" content="makeinfo 4.13"> <link title="Top" rel="start" href="index.html#Top"> <link rel="up" href="Overloading-Objects.html#Overloading-Objects" title="Overloading Objects"> <link rel="next" href="Operator-Overloading.html#Operator-Overloading" title="Operator Overloading"> <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> <meta http-equiv="Content-Style-Type" content="text/css"> <style type="text/css"><!-- pre.display { font-family:inherit } pre.format { font-family:inherit } pre.smalldisplay { font-family:inherit; font-size:smaller } pre.smallformat { font-family:inherit; font-size:smaller } pre.smallexample { font-size:smaller } pre.smalllisp { font-size:smaller } span.sc { font-variant:small-caps } span.roman { font-family:serif; font-weight:normal; } span.sansserif { font-family:sans-serif; font-weight:normal; } --></style> </head> <body> <div class="node"> <a name="Function-Overloading"></a> <p> Next: <a rel="next" accesskey="n" href="Operator-Overloading.html#Operator-Overloading">Operator Overloading</a>, Up: <a rel="up" accesskey="u" href="Overloading-Objects.html#Overloading-Objects">Overloading Objects</a> <hr> </div> <h4 class="subsection">33.4.1 Function Overloading</h4> <p>Any Octave function can be overloaded, and allows a object specific version of this function to be called as needed. A pertinent example for our polynomial class might be to overload the <code>polyval</code> function like <pre class="example"><pre class="verbatim"> function [y, dy] = polyval (p, varargin) if (nargout == 2) [y, dy] = polyval (fliplr(p.poly), varargin{:}); else y = polyval (fliplr(p.poly), varargin{:}); endif endfunction </pre> </pre> <p>This function just hands off the work to the normal Octave <code>polyval</code> function. Another interesting example for an overloaded function for our polynomial class is the <code>plot</code> function. <pre class="example"><pre class="verbatim"> 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, p(x), varargin{:}); else plot(x, p(x), varargin{:}); endif endfunction</pre> </pre> <p class="noindent">which allows polynomials to be plotted in the domain near the region of the roots of the polynomial. <p>Functions that are of particular interest to be overloaded are the class conversion functions such as <code>double</code>. Overloading these functions allows the <code>cast</code> function to work with the user class and can aid in the use of methods of other classes with the user class. An example <code>double</code> function for our polynomial class might look like. <pre class="example"><pre class="verbatim"> function b = double (a) b = a.poly; endfunction </pre> </pre> </body></html>