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| <td class="top"><a href="index.html" rel="contents">↑ Table of Contents ↑</a></td> |
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| <div class="breadcrumb"><a class="nav" href="s9.html" rel="section">§9 Value Dependent Classes</a> > <a class="nav" href="s9.2.html" rel="section">§9.2 Using classes with value parameters</a></div> |
| <div class="sect depth3" id="s9.2.1"> |
| <h3 class="sect">§9.2.1 Parameter substitution<a class="img" href="s9.2.1.html" |
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| <p>Substitution of a type anchor of a class <code>MyClass<YourType p></code> is denoted as |
| <code>MyClass<@v></code>. |
| In this term <code>v</code> must be a value which is conform to the declaration of the value |
| parameter "<code>YourType p</code>", ie., <code>v</code> must have the static type <code>YourType</code>. |
| <br /> |
| The value passed for substituting a type anchor must be a path of variables declared as <code>final</code>. |
| Obviously, only the first element in such a path can be a local variable or a method argument, |
| all other elements have to be fields. The reason for requiring final variables is |
| in type checking as discussed next. |
| |
| </p> |
| <div class="note"> |
| <h5>Note:</h5> |
| Externalized roles as defined in <a href="s1.2.2.b.html" |
| title="§1.2.2.(b) Declaration with anchored type" |
| class="sect">§1.2.2.(b)</a> are |
| a special case of types with a value parameter, where the value |
| is an instance of the enclosing team. |
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| <div class="subsect depth4" id="s9.2.1.a"> |
| <h4 class="subsect">(a) <span class="title">Instance constrained type parameters</span><a class="img" href="s9.2.1.a.html" |
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| <p>In addition to normal usage, a value parameter can be applied nested to a regular type parameter: |
| |
| </p> |
| <div class="listing plain"><pre><b>class</b> MyClass<YourType aName, DependentParam<<em>@aName></em>> { ...</pre></div> |
| <p> |
| Here the type parameter <code>DependentParam</code> is constrained to be anchored to <code>aName</code>. |
| |
| </p> |
| <p>If a value parameter is used as a constraint for a regular type parameter |
| any substitution for the type parameter must also supply a value matching the value parameter. |
| The class from above could be applied like this: |
| |
| </p> |
| <div class="listing plain"><pre><b>final</b> YourType anchor = <b>new</b> YourType(); |
| MyClass <em><@anchor, YourDependent<<strong>@anchor</strong>>></em></pre></div> |
| <p>Within the declaring element (class or method) |
| applications of the type variable representing the instance constrained type parameter |
| must repeat the anchor verbatim, i.e., no substitutions are performed here. |
| |
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| <div class="breadcrumb"><a class="nav" href="s9.html" rel="section">§9 Value Dependent Classes</a> > <a class="nav" href="s9.2.html" rel="section">§9.2 Using classes with value parameters</a></div> |
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| width="88" /></a><address>© Stephan Herrmann, Christine Hundt, Marco Mosconi</address> |
| OT/J version 1.3 — last modified: 2011-05-15 |
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