<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <!-- Created by GNU Texinfo 6.5, http://www.gnu.org/software/texinfo/ --> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>Function Overloading (GNU Octave (version 5.1.0))</title> <meta name="description" content="Function Overloading (GNU Octave (version 5.1.0))"> <meta name="keywords" content="Function Overloading (GNU Octave (version 5.1.0))"> <meta name="resource-type" content="document"> <meta name="distribution" content="global"> <meta name="Generator" content="makeinfo"> <link href="index.html#Top" rel="start" title="Top"> <link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index"> <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> <link href="Overloading-Objects.html#Overloading-Objects" rel="up" title="Overloading Objects"> <link href="Operator-Overloading.html#Operator-Overloading" rel="next" title="Operator Overloading"> <link href="Overloading-Objects.html#Overloading-Objects" rel="prev" title="Overloading Objects"> <style type="text/css"> <!-- a.summary-letter {text-decoration: none} blockquote.indentedblock {margin-right: 0em} blockquote.smallindentedblock {margin-right: 0em; font-size: smaller} blockquote.smallquotation {font-size: smaller} div.display {margin-left: 3.2em} div.example {margin-left: 3.2em} div.lisp {margin-left: 3.2em} div.smalldisplay {margin-left: 3.2em} div.smallexample {margin-left: 3.2em} div.smalllisp {margin-left: 3.2em} kbd {font-style: oblique} pre.display {font-family: inherit} pre.format {font-family: inherit} pre.menu-comment {font-family: serif} pre.menu-preformatted {font-family: serif} pre.smalldisplay {font-family: inherit; font-size: smaller} pre.smallexample {font-size: smaller} pre.smallformat {font-family: inherit; font-size: smaller} pre.smalllisp {font-size: smaller} span.nolinebreak {white-space: nowrap} span.roman {font-family: initial; font-weight: normal} span.sansserif {font-family: sans-serif; font-weight: normal} ul.no-bullet {list-style: none} --> </style> <link rel="stylesheet" type="text/css" href="octave.css"> </head> <body lang="en"> <a name="Function-Overloading"></a> <div class="header"> <p> Next: <a href="Operator-Overloading.html#Operator-Overloading" accesskey="n" rel="next">Operator Overloading</a>, Up: <a href="Overloading-Objects.html#Overloading-Objects" accesskey="u" rel="up">Overloading Objects</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p> </div> <hr> <a name="Function-Overloading-1"></a> <h4 class="subsection">34.4.1 Function Overloading</h4> <p>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 <code>polyval</code> function. </p> <div class="example"> <pre class="verbatim">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 </pre></div> <p>This function just hands off the work to the normal Octave <code>polyval</code> function. Another interesting example of an overloaded function for the polynomial class is the <code>plot</code> function. </p> <div 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, polyval (p, x), varargin{:}); else plot (x, polyval (p, x), varargin{:}); endif endfunction </pre></div> <p>which allows polynomials to be plotted in the domain near the region of the roots of the polynomial. </p> <p>Functions that are of particular interest for overloading are the class conversion functions such as <code>double</code>. Overloading these functions allows the <code>cast</code> 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 <code>double</code> function for the polynomial class might look like </p> <div class="example"> <pre class="verbatim">function a = double (p) a = p.poly; endfunction </pre></div> </body> </html>