On entry: 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 should satisfy
- $\mathit{told}\le {\mathbf{TWANT}}\le \mathrm{T}$,
or if integration is proceeding in the negative direction
- $\mathit{told}\ge {\mathbf{TWANT}}\ge \mathrm{T}$,
where
$\mathit{told}$ is the previous integration point and is, to within rounding,
TCURR –
HLAST (see
D02QXF). Extrapolation is permitted but not recommended and
${\mathbf{IFAIL}}={\mathbf{2}}$ is returned whenever extrapolation is attempted.