Re: [Help-gsl] gsl_vector_alloc question.

[John Lamb]

Sang Oh wrote:
> I'm trying to allocate memory in a function.
>
> void ruler(double xa, double xb, double dx, gsl_vector *vc) {
>  vc = gsl_vector_alloc(len);
> }

Looks like a common programming error, nothing to do with gsl. You 
cannot globally change the _value_ of a parameter. You can only change 
the value of the struct it points to. The gsl_vector_alloc call just 
changes a local copy of vc and then throws it away when the function 
returns, leaving a vector on the heap that you can't point to.

Try rewriting as

gsl_vector *ruler(double xa, double xb, double dx){
  ...
  vc = gsl_vector_alloc(len);
  ...
  return vc;
}

--
JDL