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| <td class="back"><a id="top"></a><a href="s4.4.html" rel="prev"><< §4.4 Callin parameter mapping</a></td> |
| <td class="top"><a href="index.html" rel="contents">↑ Table of Contents ↑</a></td> |
| <td class="next"><a href="s4.6.html" rel="next">§4.6 Overriding access restrictions >></a></td> |
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| <div class="breadcrumb"><a class="nav" href="s4.html" rel="section">§4 Callin Binding</a></div> |
| <div class="sect depth2" id="s4.5"> |
| <h2 class="sect">§4.5 Lifting and lowering<a class="img" href="s4.5.html" |
| title="PermaLink to §4.5 Lifting and lowering"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h2> |
| <p>For basic definition 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>. |
| <br /> |
| (The following rules are reverse forms of those from <a href="s3.3.html" title="§3.3 Lifting and lowering" class="sect">§3.3</a>) |
| |
| </p> |
| <div class="subsect depth3" id="s4.5.a"> |
| <h4 class="subsect">(a) <span class="title">Call target translation</span><a class="img" href="s4.5.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 role method due to a callin binding first |
| <strong>lifts</strong> the base object to the role class of the |
| callin binding, in order to obtain the effective call target. |
| This is why callin bindings cannot be defined in roles that are <em>unliftable</em> |
| due to <em>potential binding ambiguity</em> (see <a href="s4.1.b.html" title="§4.1.(b) Prerequisite: Class binding" |
| class="sect">§4.1.(b)</a> |
| above and <a href="s2.3.4.a.html" title="§2.3.4.(a) Potential ambiguity" |
| class="sect">§2.3.4.(a)</a>). |
| |
| </p> |
| </div> |
| <div class="subsect depth3" id="s4.5.b"> |
| <h4 class="subsect">(b) <span class="title">Parameter translation</span><a class="img" href="s4.5.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>During callin execution, each parameter for which the role method expects a role |
| object is implicitly <strong>lifted</strong> to the declared role class. |
| |
| </p> |
| </div> |
| <div class="subsect depth3" id="s4.5.c"> |
| <h4 class="subsect">(c) <span class="title">Result translation</span><a class="img" href="s4.5.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>Returning a role object from a callin method implicitly |
| <strong>lowers</strong> this object. |
| |
| </p> |
| </div> |
| <div class="subsect depth3" id="s4.5.d"> |
| <h4 class="subsect">(d) <span class="title">Typing rules</span><a class="img" href="s4.5.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 right hand side conforms to the left 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>lifting</em>;<br /> |
| however, within <code>replace</code> bindings step 1 of the smart lifting |
| algorithm (<a href="s2.3.3.a.html" title="§2.3.3.(a) Static adjustment" |
| class="sect">§2.3.3.(a)</a>) is not applicable |
| </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 left hand conforms to the |
| right hand side according to the rules given above, except that |
| translation polymorphism here applies <em>lowering</em> instead of |
| lifting. |
| </p> |
| <p> |
| These rules define <strong>translation polymorphism</strong> as introduced in |
| <a href="s2.3.html" title="§2.3 Lifting" class="sect">§2.3</a>. |
| |
| </p> |
| <p>Additionally, in a <code>replace</code> callin binding compatibility of parameters and return |
| types must hold in both directions. |
| Thus, from the above list of conversions a replace binding cannot apply subtype polymorphism |
| nor primitive type conversion. |
| If more flexibility is desired, type parameters can be used as defined in <a href="s4.10.html" title="§4.10 Generic callin bindings" |
| class="sect">§4.10</a>. |
| |
| </p> |
| </div> |
| <div class="subsect depth3" id="s4.5.e"> |
| <h4 class="subsect">(e) <span class="title">Role arrays</span><a class="img" href="s4.5.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="s2.3.d.html" title="§2.3.(d) Lifting of arrays" |
| class="sect">§2.3.(d)</a> applies |
| accordingly. For arrays as return value <a href="s2.2.e.html" title="§2.2.(e) Lowering of arrays" |
| class="sect">§2.2.(e)</a> applies. |
| |
| </p> |
| </div> |
| <div class="subsect depth3" id="s4.5.f"> |
| <h4 class="subsect">(f) <span class="title">Base calls</span><a class="img" href="s4.5.f.html" title="PermaLink to (f) Base calls"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h4> |
| <p>For base calls these rules are reversed again, i.e., a |
| base call behaves like a callout binding. |
| |
| </p> |
| </div> |
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| <td class="back"><a href="s4.4.html" rel="prev"><< §4.4 Callin parameter mapping</a></td> |
| <td class="top"><a href="index.html" rel="contents">↑ Table of Contents ↑</a></td> |
| <td class="next"><a href="s4.6.html" rel="next">§4.6 Overriding access restrictions >></a></td> |
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| <div class="breadcrumb"><a class="nav" href="s4.html" rel="section">§4 Callin Binding</a></div> |
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| OT/J version 1.3 — last modified: 2010-06-08 |
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