offset gsl_vectors and matrices

["J.Underwood" <J dot Underwood at open dot ac dot uk>]

Hi

I'm fairly new to GSL, but have been pondering the best way to have offset
vectors (and matrices) i.e. vectors (and matrices) whose index doesn't run
from 0..n-1.  This of course is trivial using standard C arrays, one simply
offsets a pointer. However offsetting the data pointer within a gsl_vector
is not a good plan, since then the functions which check for an index being
in range (eg. gsl_vector_set etc) will be scuppered.  One option would be to
extend the definition of the gsl_vector to include an "offset" variable.
Another is to define ones own pointer to the gsl_vector data pointer and
offset that, but that negates using the gsl functions, and also means one
needs to either use the stride from that vector or make (hairy) assumptions
about how the vector is located in memory. This becomes very hairy with
matrices.  Any ideas/comments/pointers/suggestions welcome.

Jonathan.