Missing types in C header files

Hi,
I'm trying to start to program with the PostgreSQL's geometric primitive
types, and have started to write some code using them (PostgreSQL
version 7.1.3, installed from source). However when I
include the file utils/geo_decls.h I get an error starting that the type
PGFunction (found in a file included from geo_decls.h) cannot be found.

I've done a search of all the header files in my installation (and also
all the source files that I compiled), and cannot find the definition of
the PGFunction type. Does anyone have any idea of where I can find this
definition, or of why it might be missing.
-- 
Tony

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Dr. Tony Griffiths
Research Fellow
Information Management Group,
Department of Computer Science,
The University of Manchester,
Oxford Road,
Manchester M13 9PL, 
United Kingdom

Tel. +44 (0) 161 275 6139
Fax +44 (0) 161 275 6236
email tony.griffiths@cs.man.ac.uk
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