Silly Newbie question

To all,<br /><br />I am brand new to writing functions for PostgreSQL and understand that this question has been asked
onehundred and one times.  Please be patient with me, I do learn quickly.<br /><br />My question is:<br /><br />I wish
tocreate a an aggregate function and have read and re-read the 34.10 section of the 8.3 documentation as well as
scannedthrough the fmgr header file.  My problem is that I know certain structures are created with the idea of
retaininginformation for use in the state function but I don't really understand which structures I should be looking
atand how to initilize them (if needed) in the sfunc.  Any pushes in the right direction would be very appreciated,  I
amusing the Version 1 calling convention.<br /><br />Thanks in advance.<br /><br />Aaron <a name="XAGGR"><span
style="font-weight:bold;"> </span><br /></a><br /><hr />Sell your car for just $30 at CarPoint.com.au. <a
href="http://a.ninemsn.com.au/b.aspx?URL=http%3A%2F%2Fsecure%2Dau%2Eimrworldwide%2Ecom%2Fcgi%2Dbin%2Fa%2Fci%5F450304%2Fet%5F2%2Fcg%5F801459%2Fpi%5F1004813%2Fai%5F859641&_t=762955845&_r=tig_OCT07&_m=EXT"
target="_new">It'ssimple!</a>