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| <td class="back"><a id="top"></a><a href="s4.3.html" rel="prev"><< §4.3 Base calls</a></td> |
| <td class="top"><a href="index.html" rel="contents">↑ Table of Contents ↑</a></td> |
| <td class="next"><a href="s4.5.html" rel="next">§4.5 Lifting and lowering >></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="s4.4"> |
| <h2 class="sect">§4.4 Callin parameter mapping<a class="img" href="s4.4.html" |
| title="PermaLink to §4.4 Callin parameter mapping"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h2> |
| <div class="subsect depth3" id="s4.4.a"> |
| <h4 class="subsect">(a) <span class="title">General case parameter mapping</span><a class="img" href="s4.4.a.html" |
| title="PermaLink to (a) General case parameter mapping"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h4> |
| <p>The rules for mapping callin parameters and result type |
| are mainly the same as for callout bindings (<a href="s3.2.html" title="§3.2 Callout parameter mapping" |
| class="sect">§3.2</a>) |
| except for reversing the <code>-></code> and <code><-</code> tokens and |
| swapping left hand side and right hand side. |
| <br /> |
| Callin bindings using <code>before</code> have no result mapping. |
| For <code>result</code> in <code>after</code> callin bindings |
| see <a href="#s4.4.c" |
| title="§4.4.(c) Mapping the result of a base method" |
| class="sect">§4.4.(c)</a> below. |
| |
| </p> |
| </div> |
| <div class="subsect depth3" id="s4.4.b"> |
| <h4 class="subsect">(b) <span class="title">Restrictions for callin replace bindings</span><a class="img" href="s4.4.b.html" |
| title="PermaLink to (b) Restrictions for callin replace bindings"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h4> |
| <p>The right-hand side of a parameter mapping may either be |
| the simple name of a base method argument without further computation, |
| or an arbitrary expression <em>not</em> containing any base method argument. |
| <br /> |
| Each base method argument must either appear as a simple name in exactly one parameter mapping |
| or not be mapped at all. In the latter case, the original argument is "tunneled" to |
| the base call, meaning, the callin method does not see the argument, but it is passed |
| to the base method as expected. |
| <br /> |
| If the base method declares a result, then |
| |
| </p> |
| <ul> |
| <li>if the role method also declares a result, <code>result</code> must be mapped to itself: |
| <br /><code>result -> result</code></li> |
| <li>if the role method does not declare a result, an arbitrary expression may be mapped to result: |
| <br /><code><em>expression</em> -> result</code><br /> |
| If in this situation no result mapping exists, the result of the base call |
| is "tunneled" and passed to the original caller (see <a href="s4.3.e.html" title="§4.3.(e) Fragile callin binding" |
| class="sect"> |
| fragile callin binding (§4.3.(e))</a> above). |
| |
| </li> |
| </ul> |
| <p>These rules ensure that these bindings are reversible |
| for the sake of base calls (<a href="s4.3.html" title="§4.3 Base calls" class="sect">§4.3</a>). |
| |
| </p> |
| <p>As stated above a fragile callin binding (<a href="s4.3.e.html" title="§4.3.(e) Fragile callin binding" |
| class="sect">§4.3.(e)</a>) |
| is not allowed with a callin method that definitely has no base call |
| (<a href="s4.3.b.html" title="§4.3.(b) Missing base call" |
| class="sect">§4.3.(b)</a>). A callin replace binding is not fragile if it provides |
| the base result using a result mapping. |
| |
| </p> |
| <p>A callin method bound with replace to a base method returning |
| void must not declare a non-void result. |
| |
| </p> |
| </div> |
| <div class="subsect depth3" id="s4.4.c"> |
| <h4 class="subsect">(c) <span class="title">Mapping the result of a base method</span><a class="img" href="s4.4.c.html" |
| title="PermaLink to (c) Mapping the result of a base method"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h4> |
| <p>In an <code>after</code> callin binding, the right-hand side |
| of a parameter mapping may use the identifier <code>result</code> |
| to refer to the result of the base method. |
| |
| </p> |
| <p> |
| An <code>after</code> callin binding |
| can, however, not <em>influence</em> the result of the base method, |
| thus mappings with the <code>-></code> token are not allowed for after callin bindings. |
| For <code>before</code> mappings using the <code>-></code> token is already ruled out by <a href="#s4.4.a" title="§4.4.(a) General case parameter mapping" |
| class="sect">§4.4.(a)</a></p> |
| </div> |
| <div class="subsect depth3" id="s4.4.d"> |
| <h4 class="subsect">(d) <span class="title">Multiple base methods</span><a class="img" href="s4.4.d.html" |
| title="PermaLink to (d) Multiple base methods"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h4> |
| <p>A callin binding listing more than one base method may use parameter |
| mappings with only the following restriction: if any base parameter should be mapped this parameter |
| must have the same name and type in all listed base method designators. |
| However, different parameter mappings for different base methods bound to the same role method |
| can be defined if separate callin bindings are used. |
| |
| </p> |
| </div> |
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| <td class="back"><a href="s4.3.html" rel="prev"><< §4.3 Base calls</a></td> |
| <td class="top"><a href="index.html" rel="contents">↑ Table of Contents ↑</a></td> |
| <td class="next"><a href="s4.5.html" rel="next">§4.5 Lifting and lowering >></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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