Provide a derivative() function for grid-functions
This MR provides a dummy derivative
of grid-functions.
Probably it is possible to provide an actual derivative but this is not the scope of this MR.
Closes #7 (closed)
This MR provides a dummy derivative
of grid-functions.
Probably it is possible to provide an actual derivative but this is not the scope of this MR.
Closes #7 (closed)