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| <td class="back"><a id="top"></a><a href="s2.3.4.a.html" rel="prev"><< §2.3.4.(a) Potential ambiguity</a></td> |
| <td class="top"><a href="index.html" rel="contents">↑ Table of Contents ↑</a></td> |
| <td class="next"><a href="s2.3.4.c.html" rel="next">§2.3.4.(c) Actual ambiguity >></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="s2.3.html" rel="section">§2.3 Lifting</a> > <a class="nav" href="s2.3.4.html" rel="section">§2.3.4 Binding ambiguities</a></div> |
| <div class="subsect depth4" id="s2.3.4.b"> |
| <h4 class="subsect">§2.3.4.(b) <span class="title">Definite ambiguity</span><a class="img" href="s2.3.4.b.html" |
| title="PermaLink to (b) Definite ambiguity"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h4> |
| <p>A <strong>definite ambiguity</strong> is given if |
| |
| </p> |
| <ul> |
| <li>the situation of potential ambiguity according to (a) |
| above is given and |
| </li> |
| <li>lifting is requested (either by method binding or explicitly |
| (<a href="s2.3.2.html" title="§2.3.2 Declared lifting" class="sect">§2.3.2</a>)) from the shared base class <code>B</code> to any role |
| class <code>R0</code> that is a common super role for <code>R1</code> and <code>R2</code>. |
| </li> |
| </ul> |
| <p>Definite binding ambiguity also occurs in cases of generic declared lifting <a href="s2.3.2.e.html" title="§2.3.2.(e) Generic declared lifting" |
| class="sect">§2.3.2.(e)</a> |
| if the specified role <code>R</code> is unbound and if two independent sub-roles <code>R1</code> and <code>R2</code> |
| exist that introduce a playedBy binding to the same base class <code>BX</code>. |
| In this case no potential ambiguity is flagged because roles <code>R1</code> and <code>R2</code> |
| have no shared bound super-role. |
| |
| </p> |
| <div class="note"> |
| <h5>Effect:</h5> |
| Code causing definite ambiguity is required to handle <code>org.objectteams.LiftingFailedException</code>. |
| |
| </div> |
| <p> |
| In cases of definite binding ambiguity lifting will indeed fail except for some corner cases. |
| Such corner cases may arise if lifting already finds an appropriate role in the cache or |
| if an (indirect) subrole of the ambiguously bound role is an unambiguous lift target for the |
| concrete type of the base object at run-time. See also <a href="s2.3.5.html" |
| title="§2.3.5 Consequences of lifting problems" |
| class="sect">§2.3.5</a>. |
| |
| </p> |
| <h5 class="listing">Example code (Definite Ambiguity):</h5> |
| <div class="listing example frame"> |
| <table class="listing"> |
| <tr class="line odd"> |
| <td class="ln">1</td> |
| <td><pre><b>team</b> <b>class</b> MyTeam {</pre></td> |
| </tr> |
| <tr class="line even"> |
| <td class="ln">2</td> |
| <td><pre> <b>public</b> <b>class</b> SuperRole <b>playedBy</b> MyBase {...}</pre></td> |
| </tr> |
| <tr class="line odd"> |
| <td class="ln">3</td> |
| <td><pre> <b>public</b> <b>class</b> SubRoleA <b>extends</b> SuperRole <b>playedBy</b> SubBase {...}</pre></td> |
| </tr> |
| <tr class="line even"> |
| <td class="ln">4</td> |
| <td><pre> <b>public</b> <b>class</b> SubRoleB <b>extends</b> SuperRole <b>playedBy</b> SubBase {...}</pre></td> |
| </tr> |
| <tr class="line odd"> |
| <td class="ln">5</td> |
| <td><pre></pre></td> |
| </tr> |
| <tr class="line even"> |
| <td class="ln">6</td> |
| <td><pre> <b>public</b> <b>void</b> useSuperRole(SubBase <b>as</b> SuperRole r) {...} <span class="comment">// <span class="error">must declare LiftingFailedException</span></span></pre></td> |
| </tr> |
| <tr class="line odd"> |
| <td class="ln">7</td> |
| <td><pre>}</pre></td> |
| </tr> |
| </table> |
| </div> |
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| <td class="back"><a href="s2.3.4.a.html" rel="prev"><< §2.3.4.(a) Potential ambiguity</a></td> |
| <td class="top"><a href="index.html" rel="contents">↑ Table of Contents ↑</a></td> |
| <td class="next"><a href="s2.3.4.c.html" rel="next">§2.3.4.(c) Actual ambiguity >></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="s2.3.html" rel="section">§2.3 Lifting</a> > <a class="nav" href="s2.3.4.html" rel="section">§2.3.4 Binding ambiguities</a></div> |
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| OT/J version 1.3 — last modified: 2011-05-15 |
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