http://wandora.org/w/index.php?action=history&feed=atom&title=Empty_%28query_directive%29
Empty (query directive) - Revision history
2026-04-18T12:02:44Z
Revision history for this page on the wiki
MediaWiki 1.19.1
http://wandora.org/w/index.php?title=Empty_(query_directive)&diff=6984&oldid=prev
Olli: /* Examples */
2009-08-25T10:23:46Z
<p><span dir="auto"><span class="autocomment">Examples</span></span></p>
<table class='diff diff-contentalign-left'>
<col class='diff-marker' />
<col class='diff-content' />
<col class='diff-marker' />
<col class='diff-content' />
<tr valign='top'>
<td colspan='2' style="background-color: white; color:black;">← Older revision</td>
<td colspan='2' style="background-color: white; color:black;">Revision as of 10:23, 25 August 2009</td>
</tr><tr><td colspan="2" class="diff-lineno">Line 15:</td>
<td colspan="2" class="diff-lineno">Line 15:</td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>  importPackage(org.wandora.query2)</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>  importPackage(org.wandora.query2)</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>  new If(</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>  new If(</div></td></tr>
<tr><td class='diff-marker'>−</td><td style="background: #ffa; color:black; font-size: smaller;"><div>   <del class="diffchange diffchange-inline">new Exists(</del>new Instances(<del class="diffchange diffchange-inline">)</del>),</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>   new Instances(),</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>   new Empty(),</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>   new Empty(),</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>   new Literals("no instances")</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>   new Literals("no instances")</div></td></tr>
</table>
Olli
http://wandora.org/w/index.php?title=Empty_(query_directive)&diff=6900&oldid=prev
Olli at 10:21, 20 August 2009
2009-08-20T10:21:39Z
<p></p>
<table class='diff diff-contentalign-left'>
<col class='diff-marker' />
<col class='diff-content' />
<col class='diff-marker' />
<col class='diff-content' />
<tr valign='top'>
<td colspan='2' style="background-color: white; color:black;">← Older revision</td>
<td colspan='2' style="background-color: white; color:black;">Revision as of 10:21, 20 August 2009</td>
</tr><tr><td colspan="2" class="diff-lineno">Line 8:</td>
<td colspan="2" class="diff-lineno">Line 8:</td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>[[Category:Query directives]]</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>[[Category:Query directives]]</div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins style="color: red; font-weight: bold; text-decoration: none;"></ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins style="color: red; font-weight: bold; text-decoration: none;">== Examples ==</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins style="color: red; font-weight: bold; text-decoration: none;"></ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins style="color: red; font-weight: bold; text-decoration: none;">''Empty'' directive doesn't have many practical uses. It can be combined for example with ''If'' directive to return an empty set in some cases. ''If'' directive does this internally if no else directive is provided. You can turn this other way round and only return something in the else part as follows.</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins style="color: red; font-weight: bold; text-decoration: none;"></ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins style="color: red; font-weight: bold; text-decoration: none;"> importPackage(org.wandora.query2)</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins style="color: red; font-weight: bold; text-decoration: none;"> new If(</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins style="color: red; font-weight: bold; text-decoration: none;">  new Exists(new Instances()),</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins style="color: red; font-weight: bold; text-decoration: none;">  new Empty(),</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins style="color: red; font-weight: bold; text-decoration: none;">  new Literals("no instances")</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins style="color: red; font-weight: bold; text-decoration: none;"> )</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins style="color: red; font-weight: bold; text-decoration: none;"></ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins style="color: red; font-weight: bold; text-decoration: none;">Of course you could achieve same thing by using ''Not'' directive in the condition.</ins></div></td></tr>
</table>
Olli
http://wandora.org/w/index.php?title=Empty_(query_directive)&diff=6863&oldid=prev
Olli at 07:45, 20 August 2009
2009-08-20T07:45:43Z
<p></p>
<p><b>New page</b></p><div>== Description ==<br />
<br />
Returns an empty result. <br />
<br />
== Constructor ==<br />
<br />
Empty() <br />
<br />
[[Category:Query directives]]</div>
Olli