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<h2>qset.c -- set data type and operations</h2>
<blockquote>
<p>Qhull's data structures are constructed from sets. The
functions and macros in qset.c construct, iterate, and
modify these sets. They are the most frequently called
functions in Qhull. For this reason, efficiency is the
primary concern. </p>
<p>In Qhull, a <i>set</i> is represented by an unordered
array of pointers with a maximum size and a NULL
terminator (<a href="qset.h#setT">setT</a>).
Most sets correspond to mathematical sets
(i.e., the pointers are unique). Some sets are sorted to
enforce uniqueness. Some sets are ordered. For example,
the order of vertices in a ridge determine the ridge's
orientation. If you reverse the order of adjacent
vertices, the orientation reverses. Some sets are not
mathematical sets. They may be indexed as an array and
they may include NULL pointers. </p>
<p>The most common operation on a set is to iterate its
members. This is done with a 'FOREACH...' macro. Each set
has a custom macro. For example, 'FOREACHvertex_'
iterates over a set of vertices. Each vertex is assigned
to the variable 'vertex' from the pointer 'vertexp'. </p>
<p>Most sets are constructed by appending elements to the
set. The last element of a set is either NULL or the
index of the terminating NULL for a partially full set.
If a set is full, appending an element copies the set to
a larger array. </p>
</blockquote>
<p><b>Copyright © 1995-2003 The Geometry Center, Minneapolis MN</b></p>
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