I am trying to write the interface to this gsl function: gsl_multifit_fdfsolver_jac (I believe introduced in gsl 2.0) that is necessary for nonlinear-least-squares.lisp

(It is returns the Jacobian) See documentation and example usage:

gsl_multifit_fdfsolver_jac(s, J);
gsl_multifit_covar (J, 0.0, covar);

This is my failed attempt after looking at gsll code and documentation

(defmfun jacobian (solver)

"gsl_multifit_fdfsolver_jac"

(((mpointer solver) :pointer) (*jacobian :pointer)

:definition :function

:inputs (solver)

:outputs (*jacobian)

:c-return :success-failure

:return ((make-foreign-array-from-mpointer *jacobian))

:documentation "Query the solver for the Jacobian, a pointer")

Can someone tell me how to make this work?

Thanks,

Mirko