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| <td class="back"><a id="top"></a><a href="s4.9.3.a.html" rel="prev"><< §4.9.3.(a) No covariant callin methods</a></td> |
| <td class="top"><a href="index.html" rel="contents">↑ Table of Contents ↑</a></td> |
| <td class="next"><a href="s4.9.3.c.html" rel="next">§4.9.3.(c) Covariant replace binding >></a></td> |
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| <div class="breadcrumb"><a class="nav" href="s4.html" rel="section">§4 Callin Binding</a> > <a class="nav" href="s4.9.html" rel="section">§4.9 Callin inheritance</a> > <a class="nav" href="s4.9.3.html" rel="section">§4.9.3 Covariant return types</a></div> |
| <div class="subsect depth4" id="s4.9.3.b"> |
| <h4 class="subsect">§4.9.3.(b) <span class="title">Capturing covariant base methods</span><a class="img" href="s4.9.3.b.html" |
| title="PermaLink to (b) Capturing covariant base methods"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
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| <p> |
| If a callin binding should indeed affect not only the specified base method |
| but also overriding versions which covariantly redefine the return type, |
| the binding must specify the base method's return type with a "+" appended |
| to the type name as in |
| </p> |
| <div class="listing plain"><pre><b>void</b> rm() <b><-</b> <b>before</b> <em>RT+</em> bm();</pre></div> |
| <p>Without the "+" sign the binding would only capture base methods whose |
| return type is exactly <code>RT</code>; |
| by appending "+" also sub-types of <code>RT</code> |
| are accepted as the declared return type. |
| |
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| <div class="breadcrumb"><a class="nav" href="s4.html" rel="section">§4 Callin Binding</a> > <a class="nav" href="s4.9.html" rel="section">§4.9 Callin inheritance</a> > <a class="nav" href="s4.9.3.html" rel="section">§4.9.3 Covariant return types</a></div> |
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