Program e01cffe

!     E01CFF Example Program Text

!     Mark 27.3 Release. NAG Copyright 2021.

!     .. Use Statements ..
      Use nag_library, Only: e01cef, e01cff, nag_wp
!     .. Implicit None Statement ..
      Implicit None
!     .. Parameters ..
      Integer, Parameter               :: nin = 5, nout = 6
!     .. Local Scalars ..
      Real (Kind=nag_wp)               :: lam
      Integer                          :: i, ifail, m, n
      Logical                          :: negfor, yfor
!     .. Local Arrays ..
      Real (Kind=nag_wp), Allocatable  :: comm(:), forval(:), intval(:), x(:), &
                                          xi(:), y(:)
!     .. Intrinsic Procedures ..
      Intrinsic                        :: real
!     .. Executable Statements ..

      Write (nout,*) 'E01CFF Example Program Results'

!     Skip heading in data file
      Read (nin,*)

!     Input the number of nodes.
      Read (nin,*) n, m

      Allocate (x(n),y(n),comm(4*n+10),xi(m),intval(m),forval(m))

!     Input whether negative forward differences are allowed, and whether
!     supplied values are forward differences
      Read (nin,*) negfor, yfor

!     Read amelioration parameter value
      Read (nin,*) lam

!     Read in data points x and y.
      Read (nin,*)(x(i),y(i),i=1,n)

!     Interpolation setup
      ifail = 0
      Call e01cef(n,lam,negfor,yfor,x,y,comm,ifail)

      forval = 0.0_nag_wp
      intval = 0.0_nag_wp

!     Interpolate at values in range [0:x(n)+0.2] in steps of 0.1
      Write (nout,99999) 'i', 'x', 'Rate', 'Forward'
      Do i = 1, m
        xi(i) = real(i,kind=nag_wp)*0.1_nag_wp - 0.1_nag_wp
      End Do
      ifail = 0
      Call e01cff(m,xi,intval,forval,comm,ifail)
      Do i = 1, m
        Write (nout,99998) i, xi(i), intval(i), forval(i)
      End Do

      Deallocate (x,y,comm,xi,intval,forval)

99999 Format (T1,A,T6,A,T13,A,T20,A)
99998 Format (I3.3,F7.2,F7.3,F7.3)

    End Program e01cffe