Hi, <br><br>I've been looking at the documentation for the graph.ss library (in MrLib 7.5) and came across some notation that I am not familiar with;<br><p>
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<a name="node_idx_310"></a><a name="node_kw_definitionadd-linksadd-links6"></a><code class="scheme">(add-links</code><tt> </tt><code class="scheme"><span class="variable"><tt><br>
<a href="http://download.plt-scheme.org/doc/371/html/mrlib/mrlib-Z-H-47.html#node_tag_Temp_43"><code class="scheme">graph-snip<%></code></a> <br>
<a href="http://download.plt-scheme.org/doc/371/html/mrlib/mrlib-Z-H-47.html#node_tag_Temp_43"><code class="scheme">graph-snip<%></code></a><br>
(union false? (is-a?/c <a href="http://download.plt-scheme.org/doc/371/html/mred/mred-Z-H-546.html#node_tag_Temp_544"><code class="scheme">pen%</code></a>))<br>
(union false? (is-a?/c <a href="http://download.plt-scheme.org/doc/371/html/mred/mred-Z-H-546.html#node_tag_Temp_544"><code class="scheme">pen%</code></a>))<br>
(union false? (is-a?/c <a href="http://download.plt-scheme.org/doc/371/html/mred/mred-Z-H-420.html#node_tag_Temp_418"><code class="scheme">brush%</code></a>))<br>
(union false? (is-a?/c <a href="http://download.plt-scheme.org/doc/371/html/mred/mred-Z-H-420.html#node_tag_Temp_418"><code class="scheme">brush%</code></a>)))</tt></span></code><code class="scheme">)</code> <small>
P</small><small>R</small><small>O</small><small>C</small><small>E</small><small>D</small><small>U</small><small>R</small><small>E</small><br></p><p>-- <a href="http://download.plt-scheme.org/doc/371/html/mrlib/mrlib-Z-H-55.html#node_sec_7.5">
http://download.plt-scheme.org/doc/371/html/mrlib/mrlib-Z-H-55.html#node_sec_7.5</a></p><p>I can tell it's asking for things that implement either a class or matching interface, <br></p><p>but the use of the 'union false?'
<br></p>Is union the one from the parser tools collection?<br><br>I'm guessing that it returns #f if the interfce isn't implemented - or do I have this all wrong.<br><br><br>Cheers,<br><br>Stephen<br><br>