Program d01gafe

!     D01GAF Example Program Text

!     Mark 27.3 Release. NAG Copyright 2021.

!     .. Use Statements ..
      Use nag_library, Only: d01gaf, nag_wp
!     .. Implicit None Statement ..
      Implicit None
!     .. Parameters ..
      Integer, Parameter               :: nin = 5, nout = 6
!     .. Local Scalars ..
      Real (Kind=nag_wp)               :: ans, er
      Integer                          :: i, ifail, n
!     .. Local Arrays ..
      Real (Kind=nag_wp), Allocatable  :: x(:), y(:)
!     .. Executable Statements ..
      Write (nout,*) 'D01GAF Example Program Results'

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

      Read (nin,*) n
      Allocate (x(n),y(n))

      Read (nin,*)(x(i),y(i),i=1,n)

      ifail = -1
      Call d01gaf(x,y,n,ans,er,ifail)

      Select Case (ifail)
      Case (0)
        Write (nout,*)
        Write (nout,99999) 'Integral = ', ans, '     Estimated error = ', er
      Case (1)
        Write (nout,*)
        Write (nout,*) 'Less than 4 points supplied'
      Case (2)
        Write (nout,*)
        Write (nout,*) 'Points not in increasing or decreasing order'
      Case (3)
        Write (nout,*)
        Write (nout,*) 'Points not all distinct'
      End Select

99999 Format (1X,A,F7.4,A,F7.4)
    End Program d01gafe