```!   E01DA_A1W_F Example Program Text
!   Mark 27 Release. NAG Copyright 2019.
Program e01da_a1w_fe

!     .. Use Statements ..
Use iso_c_binding, Only: c_ptr
Use nagad_library, Only: e01da_a1w_f, e02de_a1w_f,                       &
x10aa_a1w_f, x10ab_a1w_f, Assignment (=)
Use nag_library, Only: nag_wp, x04caf
!     .. Implicit None Statement ..
Implicit None
!     .. Parameters ..
Integer, Parameter               :: nin = 5, nout = 6
!     .. Local Scalars ..
Integer                          :: ifail, j, m, mx, my, px, py
!     .. Local Arrays ..
Type (nagad_a1w_w_rtype), Allocatable :: c(:), f(:,:), lamda(:), mu(:),  &
wrk(:), x(:), y(:)
Type (nagad_a1w_w_rtype)         :: ff(1), tx(1), ty(1)
Real (Kind=nag_wp), Allocatable  :: df(:,:), xr(:), yr(:)
Integer, Allocatable             :: iwrk(:)
!     .. Executable Statements ..
Write (nout,*) 'E01DA_A1W_F Example Program Results'

!     Skip heading in data file

!     Read the number of X points, MX, and the values of the
!     X co-ordinates.

Allocate (x(mx),xr(mx),lamda(mx+4))

x(1:mx) = xr(1:mx)

!     Read the number of Y points, MY, and the values of the
!     Y co-ordinates.

Allocate (y(my),yr(my),mu(my+4),c(mx*my),f(my,mx),wrk((mx+6)*(my+6)))
y(1:my) = yr(1:my)

!     Read the function values at the grid points.
Do j = 1, my
f(j,1:mx) = xr(1:mx)
End Do

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

!     Register variables to differentiate w.r.t.

!     Call AD Interpolating Function routine
ifail = 0

Deallocate (wrk)

!     Interpolant to be evaluated at a single point
m = 1
tx(1) = 1.4_nag_wp
ty(1) = 0.5_nag_wp

Allocate (wrk(py-4),iwrk(py-4))

ifail = 0

Write (nout,*)
Write (nout,99999) tx(1)%value, ty(1)%value
Write (nout,99998) ff(1)%value
99999 Format (1X,' Spline fitted at point x = ',F6.2,' and y = ',F6.2)
99998 Format (1X,' Value of fitted spline   = ',F7.3)

!     Setup evaluation of derivatives via adjoints

ifail = 0

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

!     Get derivatives
Allocate (df(my,mx))

Write (nout,*)
Write (nout,*) ' Derivatives of fitted value w.r.t. data points:'
Write (nout,*)
Call x04caf('General',' ',1,mx,xr,1,' dfit/dx ',ifail)

Write (nout,*)
Call x04caf('General',' ',1,my,yr,1,' dfit/dy ',ifail)

Write (nout,*)
Write (nout,*) ' Derivatives of fitted value w.r.t. f-values:'
Write (nout,*)
Call x04caf('General',' ',my,mx,df,my,' dfit/df ',ifail)

!     Remove computational data object and tape