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<H2><A NAME="SECTION00045000000000000000">
Heap data structure</A>
</H2>

<P>
Among the tools routines of sec.&nbsp;<A HREF="node70.html#sec:toolsrout">6</A>, we have a number
of sorting utilities; the heap sort is implemented in terms of heaps
having the following signatures:
<DL>
<DT><STRONG><TT>psb_T_heap</TT></STRONG></DT>
<DD>: a heap containing elements of type T, where T
  can be <code>i,s,c,d,z</code> for integer, real and complex data;
</DD>
<DT><STRONG><TT>psb_T_idx_heap</TT></STRONG></DT>
<DD>: a heap containing elements of type T, as
  above, together with an integer index.
</DD>
</DL>
Given a heap object, the following methods are defined on it:
<DL>
<DT><STRONG>init</STRONG></DT>
<DD>Initialize memory; also choose ascending or descending
  order;
</DD>
<DT><STRONG>howmany</STRONG></DT>
<DD>Current heap occupancy;
</DD>
<DT><STRONG>insert</STRONG></DT>
<DD>Add an item (or an item and its index);
</DD>
<DT><STRONG>get_first</STRONG></DT>
<DD>Remove and return the first element;
</DD>
<DT><STRONG>dump</STRONG></DT>
<DD>Print on file;
</DD>
<DT><STRONG>free</STRONG></DT>
<DD>Release memory.
</DD>
</DL>
These objects are used in MLD2P4 to implement the factorization
algorithms. 

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