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| <td class="back"><a id="top"></a><a href="s3.2.html" rel="prev"><< §3.2 Callout parameter mapping</a></td> |
| <td class="top"><a href="index.html" rel="contents">↑ Table of Contents ↑</a></td> |
| <td class="next"><a href="s3.4.html" rel="next">§3.4 Overriding access restrictions >></a></td> |
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| <div class="breadcrumb"><a class="nav" href="s3.html" rel="section">§3 Callout Binding</a></div> |
| <div class="sect depth2" id="s3.3"> |
| <h2 class="sect">§3.3 Lifting and lowering<a class="img" href="s3.3.html" |
| title="PermaLink to §3.3 Lifting and lowering"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
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| <p> (For basic definitions see <a href="s2.2.html" title="§2.2 Lowering" class="sect">§2.2</a> and <a href="s2.3.html" title="§2.3 Lifting" class="sect">§2.3</a>) |
| |
| </p> |
| <div class="subsect depth3" id="s3.3.a"> |
| <h4 class="subsect">(a) <span class="title">Call target translation</span><a class="img" href="s3.3.a.html" |
| title="PermaLink to (a) Call target translation"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h4> |
| <p>Invoking a base method due to a callout binding first |
| <strong>lowers</strong> the role object in order to obtain the effective call target. |
| |
| </p> |
| </div> |
| <div class="subsect depth3" id="s3.3.b"> |
| <h4 class="subsect">(b) <span class="title">Parameter translation</span><a class="img" href="s3.3.b.html" |
| title="PermaLink to (b) Parameter translation"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h4> |
| <p>Passing a role object as parameter to a callout method implicitly <strong>lowers</strong> |
| this parameter, if the base method declares a corresponding base type parameter. |
| <br /> |
| Lifting of callout parameters is not possible. |
| |
| </p> |
| </div> |
| <div class="subsect depth3" id="s3.3.c"> |
| <h4 class="subsect">(c) <span class="title">Result translation</span><a class="img" href="s3.3.c.html" |
| title="PermaLink to (c) Result translation"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h4> |
| <p> When returning a base object from a callout method where the role |
| method declares the result to be of a role class, |
| this object is implicitly <strong>lifted</strong> to the appropriate role. |
| <br /> |
| Lowering the result of a callout binding is not possible. |
| |
| </p> |
| </div> |
| <div class="subsect depth3" id="s3.3.d"> |
| <h4 class="subsect">(d) <span class="title">Typing rules</span><a class="img" href="s3.3.d.html" title="PermaLink to (d) Typing rules"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h4> |
| <p>A parameter mapping (implicit by parameter position or explicit |
| by a <code>with</code> clause) is <strong>well typed</strong> if |
| the left hand side conforms to the right hand side, either by |
| |
| </p> |
| <ul> |
| <li>type equality</li> |
| <li>implicit primitive type conversion</li> |
| <li>subtype polymorphism</li> |
| <li>translation polymorphism, here: <em>lowering</em>, |
| </li> |
| <li><em>or</em> by a combination of the above. |
| </li> |
| </ul> |
| <p>A result mapping (implicit or explicit by a <code>with</code> clause) |
| is well typed, if the value at the right hand side conforms to the |
| left hand side according to the rules given above, except that |
| translation polymorphism here applies <em>lifting</em> instead of |
| lowering. |
| |
| </p> |
| </div> |
| <div class="subsect depth3" id="s3.3.e"> |
| <h4 class="subsect">(e) <span class="title">Role arrays</span><a class="img" href="s3.3.e.html" title="PermaLink to (e) Role arrays"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h4> |
| <p>For arrays of roles as parameters <a href="s2.2.e.html" title="§2.2.(e) Lowering of arrays" |
| class="sect">§2.2.(e)</a> applies accordingly. |
| For arrays as a return value <a href="s2.3.d.html" title="§2.3.(d) Lifting of arrays" |
| class="sect">§2.3.(d)</a> applies. |
| |
| </p> |
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| <td class="back"><a href="s3.2.html" rel="prev"><< §3.2 Callout parameter mapping</a></td> |
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| <td class="next"><a href="s3.4.html" rel="next">§3.4 Overriding access restrictions >></a></td> |
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