: the point at which components of the solution and derivative are to be evaluated. TWANT
should not normally be an extrapolation point, that is TWANT
or if integration is proceeding in the negative direction
is the previous integration point which is held in an element of the array RWORK
and is, to within rounding,
is given by D02LYF
.) Extrapolation is permitted but not recommended, and
is returned whenever extrapolation is attempted.