d                       Differentiate a function for a single variable.
fcts                    S4 class _fcts_
fcts_add_fct            appending a S4 class of type _fcts_
gradient                Compute the gradient-function of a function.
hessian                 Compute the Hessian-function of a function.
jacobian                jacobian function
simplify                Simplify an expression by computing the values
                        for constant expressions
