[Proj] Verification of inverse step in projection

[José Luis García Pallero]

2009/12/13 Roger Oberholtzer <roger at opq.se>:
>
> On Dec 13, 2009, at 3:25 PM, José Luis García Pallero wrote:
>
>> 2009/12/13 Roger Oberholtzer <roger at opq.se>:
>>> Perhaps:
>>>
>>> projPJ *pjStruct;
>>>
>>> as pj_init_plus returns a pointer.
>>>
>>>
>>>> pjStruct = pj_init_plus("+proj=tcc +ellps=clrk66 +lon_0=90W");
>>>> if(!pjStruct)
>>>>    ....
>>>> if(pjStruct->inv==0)
>>>>    ....
>>
>> But pj_init_plus() can't know if you will use the forward or the
>> inverse step.
>
> These are two different issues:
>
> 1) You have a syntax error, which I tried to explain. That must be
> corrected no matter.

But the correct way of projPJ declaration is projPJ pjStruct because,
actually, projPJ is internally a pointer, as you can see in
http://trac.osgeo.org/proj/browser/trunk/proj/src/proj_api.h#L53
My problem is that I need to know if any projection has inverse step,
because some of them have not. As I posted in my first message, the
PROJ4 manual says that this can be checked as pjStruct->inv==0
(inverse step do not exist). But my compiler says that the member
'inv' do not exists in pjStruct.

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José Luis García Pallero
jgpallero at gmail.com
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