[Help-gsl] Re: Declaring GSL_Vector Globally

[Matthew Boulton]

After some work I've been able to find a solution so I thought I'd post 
it up in case anyone else ever has the same question:

Basically I created a main function and a secondary function that 
altered one of the vectors to check that the vector was truly global. 
The declarations at the beginning of each file are a slight pain, but 
these can easily be incorporated into a custom header file.

--main.c:

#include <stdio.h>
#include <gsl/gsl_vector.h>

gsl_vector *v1;
gsl_vector *v2;

/* Declare functions */

void alter_vec();

/* Main function */

int main()

{

 int ncomp;

 ncomp = 1;

 v1 = gsl_vector_calloc( ncomp + 1 + 100 );
 v2 = gsl_vector_calloc( ncomp + 1 + 100 );

 gsl_vector_set_all( v1 , 10.0 );
 gsl_vector_set_all( v2 , 20.0 );

 alter_vec();

 gsl_vector_fprintf( stdout , v1 , "%g" );
 gsl_vector_fprintf( stdout , v2 , "%g" );

 return 0;

}


--alter_vec.c

#include <stdio.h>
#include <gsl/gsl_vector.h>

gsl_vector *v1;
gsl_vector *v2;

void alter_vec() /* Code altering v1 */

{

 gsl_vector_set_all( v1 , 30.0 );

 return;

}


Kind Regards,

Matt


Matthew Boulton wrote:
> Hello. Is it possible to declare a GSL Vector globally without 
> declaring it at the very beginning of the code before main?
>
> Basically I have tried using extern as I usually do with integer 
> variables, however since the GSL Vector seems to be declared and 
> initialised all in one line, I can't seem to declare it at the 
> beginning of the code, then declare it as external when I initialise 
> it. For example:
>
> #include <stdio.h>
>
> int num;
>
> int main()
>
> {
>
>  extern int num;
>  num = 10;
>  return 0;
>
> }
>
> is my usual method, but using this with GSL vectors as follows:
>
> #include <stdio.h>
> #include <gsl/gsl_vector.h>
>
> gsl_vector *check_vec;
>
> int main()
>
> {
>
>  int ncomp;
>
>  ncomp = 100;
>
>  extern gsl_vector *check_vec = gsl_vector_calloc( ncomp + 1 + 100 );
>  return 0;
>
> }
>
> will not work.
>
> Kind Regards,
>
> Matt