anchor.diff:      (setf (mem-aref grad_f :double i) 0d0))
     (setf (mem-aref grad_f :double (1- n)) 1d0)
     1)
  -  
  +
   (defclass sail-data ()
     ((mu :initarg :mu)
      (lightness :initarg :lightness)
  
positive.code: 
  	;; Solve problem
  	(ipoptsolve nlp x (null-pointer) obj (null-pointer) mult_x_l mult_x_u (null-pointer))
  	))))
  
negative.code:       (let ((nlp (createipoptproblem n x_l x_u m g_l g_u (length (jacobian-structure m n)) (length (hessian-structure n)) 0 (callback sail2d_f) (callback sail2d_g) (callback sail2d_grad_f) (callback sail2d_jac_g) (callback sail2d_h))))
  
  	;; Set options
  	;;(addipoptnumoption nlp "tol" 1d-9)
  	(addipoptintoption nlp "max_iter" 1000)
  	;;(addipoptstroption nlp "mu_strategy" "adaptive")
  	;;(addipoptstroption nlp "hessian_approximation" "limited-memory")
  	(addipoptstroption nlp "jacobian_approximation" "finite-difference-values")
  	
  