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| <td class="back"><a id="top"></a><a href="s2.7.c.html" rel="prev"><< §2.7.(c) Layering</a></td> |
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| <div class="breadcrumb"><a class="nav" href="s2.html" rel="section">§2 Role Binding</a> > <a class="nav" href="s2.7.html" rel="section">§2.7 Advanced structures</a></div> |
| <div class="subsect depth3" id="s2.7.d"> |
| <h4 class="subsect">§2.7.(d) <span class="title">Implicit playedBy specialization</span><a class="img" href="s2.7.d.html" |
| title="PermaLink to (d) Implicit playedBy specialization"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
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| <p>According to <a href="s2.1.d.html" title="§2.1.(d) No-variance" class="sect">§2.1.(d)</a> an implicit sub-role may <em>implicitly</em> specialize an existing <code>playedBy</code> relation. |
| This requires the base class to be specified relative to some implicit (<code>OuterTeam.this</code>) or explicit (<code>OuterTeam.base</code>) team anchor. |
| Specializing that team anchor automatically specializes the playedBy declaration, too. |
| This rule never requires any action from a programmer but only explains the interpretation of a playedBy declaration in |
| complex situations. |
| |
| </p> |
| <h5>Two advanced examples demonstrating the above are:</h5> |
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| <ul> |
| <li>If a role <code>TOuter1.T.R</code> of a <strong>nested team </strong><code>TOuter1.T</code> is played by |
| another role of the outer enclosing team <code>TOuter1.B</code>, subclassing the outer team <code>TOuter1</code> to <code>TOuter2</code> |
| will produce a new role <code>TOuter2.T.R</code> which is automatically played by <code>TOuter2.B</code>, |
| an implicit sub class of the original base class <code>TOuter1.B</code>. |
| </li> |
| </ul> |
| </td> |
| <td rowspan="1" colspan="1"><img src="../images/implicitly_overriding_playedby.png" |
| alt="Implicitly overriding playedBy" /></td> |
| </tr> |
| <tr> |
| <td rowspan="1" colspan="1"> |
| <ul> |
| <li>Consider the case where a <strong>nested </strong><code>T1</code> as a role of <code>TOuter</code> is <strong>stacked</strong> |
| on a base team <code>TB1</code>. Also, <code>T1</code> is a <strong>layered team</strong> over <code>TB1</code> |
| because its role <code>R</code> adapts role <code>TB1.B</code>. |
| <br /> |
| In this situation the playedBy relation of role <code>TOuter.T1.R</code> is given by a base-anchored type <code>B<@T1.base></code>. |
| If furthermore <code>TOuter.T1</code> is subclassed to <code>TOuter.T2</code> which covariantly refines the inherited |
| playedBy declaration to <code>TB2</code>, then <code>TOuter.T2.R</code> will automatically refine the inherited playedBy relation |
| to <code>TB2.B</code> to follow the new interpretation of the <code>base</code> anchor. |
| </li> |
| </ul> |
| </td> |
| <td rowspan="1" colspan="1"><img src="../images/implicitly_overriding_playedby_base.png" |
| alt="Implicitly overriding playedBy base" /></td> |
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