[Proj] Verification of inverse step in projection

[José Luis García Pallero]

Hi,
I'm a new proj user and I have a doubt about the verification of
inverse step in projection. As the manual says (proj.4.3.pdf, page
41):

"Some projections do not have inverse capability; a state that can be
determined by proj->inv==0."

But when I try to test:

#include<proj_api.h>
......
projPJ pjStruct;
pjStruct = pj_init_plus("+proj=tcc +ellps=clrk66 +lon_0=90W");
if(!pjStruct)
    ....
if(pjStruct->inv==0)
    ....

At compilation time I obtain the error:

prueba.c: In function ‘main’:
prueba.c:22: warning: dereferencing ‘void *’ pointer
prueba.c:22: error: request for member ‘inv’ in something not a
structure or union

It says that inv is not a member of the projectios struct.
What is the correct way to check if a projection has inverse step?

Thanks

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José Luis García Pallero
jgpallero at gmail.com
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