Re: [Plplot-devel] Vector plot in curve coordinate

[Arjen M. <arj...@wl...>]

Andrew Ross wrote:

>On Wed, Dec 12, 2007 at 09:20:46AM +0100, Arjen Markus wrote:
>  
>
>>Andrew Ross wrote:
>>
>>    
>>
>>>plvec2 is equivalent to calling plvect with the pltr2 function as the
>>>pltr. This only affects the location of the vectors, not the direction /
>>>magnitude. 
>>>
>>>The only reason for plvec2 etc is that fortran (and several other bindings)
>>>don't allow you to pass a function name as an argument. They provided a
>>>limited subset of the possible functionality of plvect.
>>> 
>>>
>>>      
>>>
>>Hello Andrew,
>>
>>is that the reason for plvec2? Because Fortran, ever since it supported 
>>user-defined
>>functions, so at least from FORTRAN IV onwards, has supported passing
>>function names as arguments. There is an important limitation vis-a-vis 
>>the _data_
>>that you can pass - that is: no equivalent to (void *) types, but 
>>function names are
>>no problem at all!
>>    
>>
>
>As far as I understand it, this was the issue. Remeber that the function
>has to be converted to a C function argument that can be passed to the C
>API of the plplot library, and not just called by other fortran code. 
>Can this be done? 
>  
>
Yes, it can. I do not have the source code at hand right now, but I 
remember
doing just that for the Fortran 90 interface - for plmap(), IIRC. I 
wrote a small C wrapper that gets
the function name/address and then calls the Fortran routine. It was a 
bit tricky because
of different calling conventions on Windows, but with such a wrapper it 
is quite possible.

Regards,

Arjen