`removeduplicates`

Creates a new list by removing any duplicate items from an existing list.
If any item in the original list occurs more than once, the first instance only is kept. Otherwise, the ordering of items is preserved.
<?xml version="1.0" encoding="UTF-8"?>
<RuleSet name="Example_removeduplicates"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:noNamespaceSchemaLocation=
"http://www.curamsoftware.com/CreoleRulesSchema.xsd">
  <Class name="Person">

    <!-- The list of relationships where
         this person is the "fromPerson". -->
    <Attribute name="relationships">
      <type>
        <javaclass name="List">
          <ruleclass name="Relationship"/>
        </javaclass>
      </type>
      <derivation>
        <specified/>
      </derivation>
    </Attribute>

    <!-- The people who are related to this person.

         Any relative appears in this list only once,
         even though one person can be
         related to another in more than one way, e.g.
         my grandparent can also be my legal guardian.-->
    <Attribute name="uniqueRelatives">
      <type>
        <javaclass name="List">
          <ruleclass name="Person"/>
        </javaclass>
      </type>
      <derivation>
        <removeduplicates>
          <reference attribute="allRelatives"/>
        </removeduplicates>
      </derivation>
    </Attribute>

    <Attribute name="allRelatives">
      <type>
        <javaclass name="List">
          <ruleclass name="Person"/>
        </javaclass>
      </type>
      <derivation>
        <!-- get the relatives of this person by forming a
             list of the "toPerson" on the other end of each
             relationship. -->
        <dynamiclist>
          <list>
            <reference attribute="relationships"/>
          </list>
          <listitemexpression>
            <reference attribute="toPerson">
              <current/>
            </reference>
          </listitemexpression>
        </dynamiclist>
      </derivation>
    </Attribute>

  </Class>

  <!-- A relationship from one person to another. -->
  <Class name="Relationship">

    <Attribute name="fromPerson">
      <type>
        <ruleclass name="Person"/>
      </type>
      <derivation>
        <specified/>
      </derivation>
    </Attribute>

    <Attribute name="relationshipType">
      <type>
        <javaclass name="String"/>
      </type>
      <derivation>
        <specified/>
      </derivation>
    </Attribute>


    <Attribute name="toPerson">
      <type>
        <ruleclass name="Person"/>
      </type>
      <derivation>
        <specified/>
      </derivation>
    </Attribute>

  </Class>

</RuleSet>