<html> <head> <!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc --> <title>Values</title> <link rel="stylesheet" href="theme/style.css" type="text/css"> <link rel="prev" href="arguments.html"> <link rel="next" href="variables.html"> </head> <body> <table width="100%" height="48" border="0" background="theme/bkd2.gif" cellspacing="2"> <tr> <td width="10"> </td> <td width="85%"> <font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Values</b></font> </td> <td width="112"><a href="http://spirit.sf.net"><img src="theme/spirit.gif" align="right" border="0"></a></td> </tr> </table> <br> <table border="0"> <tr> <td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td> <td width="30"><a href="arguments.html"><img src="theme/l_arr.gif" border="0"></a></td> <td width="20"><a href="variables.html"><img src="theme/r_arr.gif" border="0"></a></td> </tr> </table> <p> Whenever we see a constant in a curryable-function such as the plus above, an actor<value<T> > (where T is the type of the constant) is, by default, automatically created for us. For instance, the example plus above is actually equivalent to:</p> <code><pre> <span class=identifier>plus</span><span class=special>(</span><span class=identifier>arg1</span><span class=special>, </span><span class=identifier>actor</span><span class=special><</span><span class=identifier>value</span><span class=special><</span><span class=keyword>int</span><span class=special>> >(</span><span class=identifier>value</span><span class=special><</span><span class=keyword>int</span><span class=special>>(</span><span class=number>6</span><span class=special>))) </span></pre></code> <p> A nifty shortcut is the val(v) utility function. The expression above is also equivalent to:</p> <code><pre> <span class=identifier>plus</span><span class=special>(</span><span class=identifier>arg1</span><span class=special>, </span><span class=identifier>val</span><span class=special>(</span><span class=number>6</span><span class=special>)) </span></pre></code> <p> actor<value<int> >(value<int>(6)) is implicitly created behind the scenes, so there's really no need to explicitly type everything but:</p> <code><pre> <span class=identifier>plus</span><span class=special>(</span><span class=identifier>arg1</span><span class=special>, </span><span class=number>6</span><span class=special>) </span></pre></code> <p> There are situations though, as we'll see later on, where we might want to explicily write val(x).</p> <p> Like arguments, values are also actors. As such, values can be evaluated through the actor's operator(). Such invocation gives the value's identity. Example:</p> <code><pre> <span class=identifier>cout </span><span class=special><< </span><span class=identifier>val</span><span class=special>(</span><span class=number>3</span><span class=special>)() << </span><span class=identifier>val</span><span class=special>(</span><span class=string>"Hello World"</span><span class=special>)(); </span><span class=identifier>prints </span><span class=identifier>out </span><span class=string>"3 Hello World"</span><span class=special>. </span></pre></code> <table border="0"> <tr> <td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td> <td width="30"><a href="arguments.html"><img src="theme/l_arr.gif" border="0"></a></td> <td width="20"><a href="variables.html"><img src="theme/r_arr.gif" border="0"></a></td> </tr> </table> <br> <hr size="1"> <p class="copyright">Copyright © 2001-2002 Joel de Guzman<br> <br> <font size="2">Use, modification and distribution is subject to the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) </font> </p> </body> </html>