anchor.diff:    (newtonmaterialgetcontactfaceattribute
      (%material-pair-ptr material-pair)))
   
  -(defun material-pair-contact-force (material-pair body)
  +(defn material-pair-contact-force ((material-pair material-pair)
  +                                   (body body))
  +    single-float
     (declare (optimize (speed 3) (safety 1) (debug 1)))
     (with-foreign-object (force :float)
       (newtonmaterialgetcontactforce
  
positive.code:      (%body-ptr body) pos3 norm3)
      (ptr->v3 norm3)))
  
  (defun (setf material-pair-contact-position) (pos3 material-pair)
    (declare (optimize (speed 3) (safety 1) (debug 1)))
    (with-foreign-array (p3 pos3 '(:array :float 3))
      (newtonmaterialsetcontactposition
  
negative.code:    material-a
     material-b
     state)
    nil)
  
  (defn world-set-default-material-elasticity (world
                                               (material-a (signed-byte 32))
                                               (material-b (signed-byte 32))
                                               (elasticity single-float))
      null
    (declare (optimize (speed 3) (safety 1) (debug 1)))
    (newtonmaterialsetdefaultelasticity
     (%world-ptr world)
     material-a
     material-b
     elasticity)
    nil)
  
  (defn world-set-default-material-friction
      ((world world)
       (material-a (signed-byte 32))
       (material-b (signed-byte 32))
       (static-friction-coefficient single-float)
       (kinetic-friction-coefficient single-float))
      null
    (declare (optimize (speed 3) (safety 1) (debug 1)))
    (newtonmaterialsetdefaultfriction
     (%world-ptr world)
  