Wrong values in GEOSCoordSeq

[Giacomo Piva]

Hi All,

I'm using for the first time GEOS library in a (ANSI) C application.
I need to get the intersection of two polygons.
Looking at the geos.h file (for C reference) I'm trying to get the
intersection in this way:

    GEOSCoordSeq coordseq = NULL;
    GEOSGeom area1 = NULL, shell = NULL, intersection = NULL;
    GEOSGeom holes_ptr[1];

    coordseq = (GEOSCoordSeq) GEOSCoordSeq_create(5, 2);    // 5 points
2 dimensions

    GEOSCoordSeq_setX(coordseq, 0, Lon_UL);    //Coord upper left
    GEOSCoordSeq_setY(coordseq, 0, Lat_UL);
    GEOSCoordSeq_setX(coordseq, 1, Lon_LR);    //Coord upper right
    GEOSCoordSeq_setY(coordseq, 1, Lat_UL);
    GEOSCoordSeq_setX(coordseq, 2, Lon_LR);    //Coord lower right
    GEOSCoordSeq_setY(coordseq, 2, Lat_LR);
    GEOSCoordSeq_setX(coordseq, 3, Lon_UL);    //Coord lower left
    GEOSCoordSeq_setY(coordseq, 3, Lat_LR);
    GEOSCoordSeq_setX(coordseq, 4, Lon_UL);    //Coord upper left (again)
    GEOSCoordSeq_setY(coordseq, 4, Lat_UL);

where Lon_* and Lat_* are float values.

First of all, I'm trying to see if the value in the coordseq are stored
properly so...

I print the inserted value:  

printf("%f \n", Lon_UL);
...

And the stored values:

for(...
    GEOSCoordSeq_getX(coordseq, i, &pippo);
    printf("[%d] %f ", i, pippo);


Finally, I get different values:
At runtime:

-131.799500

[0] -0.000000 -0.000000
[1] -0.000000 -0.000000
[2] -0.000000 -0.000000
[3] -0.000000 -0.000000
[4] -0.000000 -0.000000


I'm sorry for this stupid question but... what it's wrong?
Thanks to all.

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[Giacomo Piva]

I'm sorry, I forgot the initGEOS() call.
I'm a donkey ;)

> Hi All,
>
> I'm using for the first time GEOS library in a (ANSI) C application.
> I need to get the intersection of two polygons.
> Looking at the geos.h file (for C reference) I'm trying to get the
> intersection in this way:
>
>    GEOSCoordSeq coordseq = NULL;
>    GEOSGeom area1 = NULL, shell = NULL, intersection = NULL;
>    GEOSGeom holes_ptr[1];
>
>    coordseq = (GEOSCoordSeq) GEOSCoordSeq_create(5, 2);    // 5 points
> 2 dimensions
>
>    GEOSCoordSeq_setX(coordseq, 0, Lon_UL);    //Coord upper left
>    GEOSCoordSeq_setY(coordseq, 0, Lat_UL);
>    GEOSCoordSeq_setX(coordseq, 1, Lon_LR);    //Coord upper right
>    GEOSCoordSeq_setY(coordseq, 1, Lat_UL);
>    GEOSCoordSeq_setX(coordseq, 2, Lon_LR);    //Coord lower right
>    GEOSCoordSeq_setY(coordseq, 2, Lat_LR);
>    GEOSCoordSeq_setX(coordseq, 3, Lon_UL);    //Coord lower left
>    GEOSCoordSeq_setY(coordseq, 3, Lat_LR);
>    GEOSCoordSeq_setX(coordseq, 4, Lon_UL);    //Coord upper left (again)
>    GEOSCoordSeq_setY(coordseq, 4, Lat_UL);
>
> where Lon_* and Lat_* are float values.
>
> First of all, I'm trying to see if the value in the coordseq are
> stored properly so...
>
> I print the inserted value:
> printf("%f \n", Lon_UL);
> ...
>
> And the stored values:
>
> for(...
>    GEOSCoordSeq_getX(coordseq, i, &pippo);
>    printf("[%d] %f ", i, pippo);
>
>
> Finally, I get different values:
> At runtime:
>
> -131.799500
>
> [0] -0.000000 -0.000000
> [1] -0.000000 -0.000000
> [2] -0.000000 -0.000000
> [3] -0.000000 -0.000000
> [4] -0.000000 -0.000000
>
>
> I'm sorry for this stupid question but... what it's wrong?
> Thanks to all.
>
> _______________________________________________
> geos-devel mailing list
> [hidden email]
> http://lists.osgeo.org/mailman/listinfo/geos-devel
>
>

--
Giacomo Piva

MEEO S.r.l.
Via Saragat 9
I-44122 Ferrara, Italy
Tel: [phone]
Fax: [phone]
http://www.meeo.it

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