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<td class="back"><a id="top"></a><a href="s3.2.html" rel="prev">&lt;&lt;&nbsp;&sect;3.2&nbsp;Callout parameter mapping</a></td>
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<div class="breadcrumb"><a class="nav" href="s3.html" rel="section">&sect;3&nbsp;Callout Binding</a></div>
<div class="sect depth2" id="s3.3">
<h2 class="sect">&sect;3.3&nbsp;Lifting and lowering<a class="img" href="s3.3.html"
title="PermaLink to &sect;3.3&nbsp;Lifting and lowering"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png"
alt="" /></a></h2>
<p> (For basic definitions see <a href="s2.2.html" title="&sect;2.2&nbsp;Lowering" class="sect">&sect;2.2</a> and <a href="s2.3.html" title="&sect;2.3&nbsp;Lifting" class="sect">&sect;2.3</a>)
</p>
<div class="subsect depth3" id="s3.3.a">
<h4 class="subsect">(a)&nbsp;<span class="title">Call target translation</span><a class="img" href="s3.3.a.html"
title="PermaLink to (a)&nbsp;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)&nbsp;<span class="title">Parameter translation</span><a class="img" href="s3.3.b.html"
title="PermaLink to (b)&nbsp;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)&nbsp;<span class="title">Result translation</span><a class="img" href="s3.3.c.html"
title="PermaLink to (c)&nbsp;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>
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<div class="subsect depth3" id="s3.3.d">
<h4 class="subsect">(d)&nbsp;<span class="title">Typing rules</span><a class="img" href="s3.3.d.html" title="PermaLink to (d)&nbsp;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>
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<div class="subsect depth3" id="s3.3.e">
<h4 class="subsect">(e)&nbsp;<span class="title">Role arrays</span><a class="img" href="s3.3.e.html" title="PermaLink to (e)&nbsp;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="&sect;2.2.(e)&nbsp;Lowering of arrays"
class="sect">&sect;2.2.(e)</a> applies accordingly.
For arrays as a return value <a href="s2.3.d.html" title="&sect;2.3.(d)&nbsp;Lifting of arrays"
class="sect">&sect;2.3.(d)</a> applies.
</p>
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<td class="back"><a href="s3.2.html" rel="prev">&lt;&lt;&nbsp;&sect;3.2&nbsp;Callout parameter mapping</a></td>
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