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| <font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Values</b></font> |
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| <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> |
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| 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> |
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| <p class="copyright">Copyright © 2001-2002 Joel de Guzman<br> |
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| <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> |
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