projects / ceph.git / blame
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| 7c673cae FG |
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| 3 | <!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc --> | |
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| 15 | <font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Values</b></font> | |
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| 27 | </table> | |
| 28 | <p> | |
| 29 | 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> | |
| 30 | <code><pre> | |
| 31 | <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>))) | |
| 32 | </span></pre></code> | |
| 33 | <p> | |
| 34 | A nifty shortcut is the val(v) utility function. The expression above is also equivalent to:</p> | |
| 35 | <code><pre> | |
| 36 | <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>)) | |
| 37 | </span></pre></code> | |
| 38 | <p> | |
| 39 | actor<value<int> >(value<int>(6)) is implicitly created behind the scenes, so there's really no need to explicitly type everything but:</p> | |
| 40 | <code><pre> | |
| 41 | <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>) | |
| 42 | </span></pre></code> | |
| 43 | <p> | |
| 44 | There are situations though, as we'll see later on, where we might want to explicily write val(x).</p> | |
| 45 | <p> | |
| 46 | 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> | |
| 47 | <code><pre> | |
| 48 | <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>)(); | |
| 49 | ||
| 50 | </span><span class=identifier>prints </span><span class=identifier>out </span><span class=string>"3 Hello World"</span><span class=special>. | |
| 51 | </span></pre></code> | |
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| 57 | </tr> | |
| 58 | </table> | |
| 59 | <br> | |
| 60 | <hr size="1"> | |
| 61 | <p class="copyright">Copyright © 2001-2002 Joel de Guzman<br> | |
| 62 | <br> | |
| 63 | <font size="2">Use, modification and distribution is subject to the Boost Software | |
| 64 | License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at | |
| 65 | http://www.boost.org/LICENSE_1_0.txt) </font> </p> | |
| 66 | </body> | |
| 67 | </html> |