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Problem with C functions ?

From: Manuel Weindorf <weindorf(at)ipf(dot)uni-karlsruhe(dot)de>
To: pgsql-interfaces(at)postgresql(dot)org
Subject: Problem with C functions ?
Date: 1999-11-12 09:47:55
Message-ID: 382BE24B.C370A0ED@ipf.uni-karlsruhe.de (view raw or flat)
Thread:
Lists: pgsql-interfaces
Hi there,

I compiled a C-funtion to compute the azimuth of a LSEG but the function
never
returns the correct value, but elog( ... ) report the correct value.
So there seems to be a problem returning doubles or floats ??

compile the folling function with
gcc -fPIC -O2 -shared  -o lseg_azimuth.o -c lseg_azimuth.c
-I/opt/local/postgres/include -L/opt/local/postgres/lib
ld -G -Bdynamic -o libgeom.so   lseg_azimuth.o 

#include <math.h>

#include "postgres.h"
#include "utils/geo_decls.h"

double lseg_azimuth( LSEG* lseg );
float add_one( float arg );

double lseg_azimuth( LSEG* lseg )
{
  double x1, y1;
  double x2, y2;
  double ori;

  x1 = lseg->p[0].x;
  y1 = lseg->p[0].y;

  x2 = lseg->p[1].x;
  y2 = lseg->p[1].y;

  ori = atan2( (x2-x1), (y2-y1));
  ori = (ori / M_PI) * 200.0;

  if ( ori < 0.0 )
    ori += 400.0;

  elog( NOTICE, "ori = %8.3lf", ori );

  return( ori );  
}


then use:

create function lseg_azimuth(lseg) returns float8
  as ' ... path to the shared lib you just created ...' language 'c';


create table xxx (geometry lseg);

insert into xxx (geometry) values
('[(4148.675,5414.255),(4151.405,5414.255)]');

select lseg_azimuth(geometry) from xxx;

will return:

NOTICE:  ori =  100.000
lseg_azimuth
------------
    4148.675
(1 row)

But that's obviously not what it should be ...

Maybe you have any suggestions ?

many thanks
Manuel
-- 
Manuel Weindorf (weindorf(at)ipf(dot)bau-verm(dot)uni-karlsruhe(dot)de)
Institut fuer Photogrammetrie und Fernerkundung, Universitaet Karlsruhe
Postfach 6980 D-76128 Karlsruhe Tel. +49721 6086010 Fax +49721 694568
http://www-ipf.bau-verm.uni-karlsruhe.de

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