===============================================================================
HELP FOR: difftool
===============================================================================

CALLING SEQUENCE:  readlib ( grtools ):
                   difftool ( function ):

      PARAMETERS:  function - a function involving derivatives

-------------------------------------------------------------------------------
SYNOPSIS:

- difftool converts the active form diff to Diff for any second
  order or higher derivatives but NOT for first order derivatives.
  This allows the user to set first order derivatives to zero
  without affecting higher order derivatives.

- difftool is part of the grtools library. Before this command can be
  used, this library must be loaded via readlib(grtools).

- To apply this to GRTensorII objects use grmap().

-------------------------------------------------------------------------------
EXAMPLE:

> readlib ( grtools ):
> diff ( R(r,t), r ) + diff ( diff( R(r,t), r ),t );

                                        /    2          \
                       /  d         \   |   d           |
                       |---- R(r, t)| + |------- R(r, t)|
                       \ dr         /   \ dt dr         /

> lprint ( difftool(") );

diff(R(r,t),r)+Diff(Diff(R(r,t),r),t)

-------------------------------------------------------------------------------
SEE ALSO: diff, Diff, grmap.
===============================================================================