NAG Library Manual, Mark 27.3
```!   E01BA_T1W_F Example Program Text
!   Mark 27.3 Release. NAG Copyright 2021.
Program e01ba_t1w_fe

!     .. Use Statements ..
Use iso_c_binding, Only: c_ptr
Use nagad_library, Only: e01ba_t1w_f, e02bb_t1w_f, exp,                  &
x10aa_t1w_f, x10ab_t1w_f, Assignment (=)
Use nag_library, Only: nag_wp
!     .. Implicit None Statement ..
Implicit None
!     .. Parameters ..
Integer, Parameter               :: m = 7, nout = 6
Integer, Parameter               :: lck = m + 4
Integer, Parameter               :: lwrk = 6*m + 16
Real (Kind=nag_wp), Parameter    :: xc(m) = (/0.0_nag_wp,0.2_nag_wp,     &
0.4_nag_wp,0.6_nag_wp,0.75_nag_wp,   &
0.9_nag_wp,1.0_nag_wp/)
!     .. Local Scalars ..
Integer                          :: i, ifail, j
!     .. Local Arrays ..
Type (nagad_t1w_w_rtype)         :: c(lck), lamda(lck), wrk(lwrk), x(m), &
y(m)
Real (Kind=nag_wp)               :: dx(m), dy(m)
!     .. Executable Statements ..
Write (nout,*) 'E01BA_T1W_F Example Program Results'

!     Create AD configuration data object and set computational mode
ifail = 0

x(1:m) = xc(1:m)
y(1:m) = exp(x(1:m))

xint = 0.5_nag_wp
Do i = 1, 2*m

If (i<=m) Then
Else
End If

c = 0.0_nag_wp

ifail = 0

!       Call Use spline computed by e01ba to fit value at x = 0.5 using e02bb
fit = 0.0_nag_wp
ifail = 0

If (i<=m) Then
dx(i) = fit%tangent
x(i)%tangent = 0.0_nag_wp
Else
dy(i-m) = fit%tangent
y(i-m)%tangent = 0.0_nag_wp
End If

End Do

Write (nout,*)
Write (nout,99999) xint%value, fit%value
99999 Format (1X,' Value of fitted spline at x = ',F6.2,', is: ',F7.4)

Write (nout,*)
Write (nout,*) ' Derivatives calculated: First order tangents'
Write (nout,*) ' Computational mode    : algorithmic'

Write (nout,*)
Write (nout,*) ' Derivatives of fitted value w.r.t. data points:'
Write (nout,*) '  j    d/dx(j)      d/y(j)'
Do j = 1, m
Write (nout,99998) j, dx(j), dy(j)
End Do
99998 Format (1X,I3,1X,E12.5,1X,E12.5)

!     Remove computational data object