!   D01AHF Example Program Text
!   Mark 27.3 Release. NAG Copyright 2021.

    Module d01ahfe_mod

!     D01AHF Example Program Module:
!            Parameters and User-defined Routines

!     .. Use Statements ..
      Use nag_library, Only: nag_wp
!     .. Implicit None Statement ..
      Implicit None
!     .. Accessibility Statements ..
      Private
      Public                           :: f
!     .. Parameters ..
      Integer, Parameter, Public       :: nin = 5, nout = 6
    Contains
      Function f(x)

!       .. Function Return Value ..
        Real (Kind=nag_wp)             :: f
!       .. Scalar Arguments ..
        Real (Kind=nag_wp), Intent (In) :: x
!       .. Executable Statements ..
        f = 4.0E0_nag_wp/(1.0E0_nag_wp+x*x)

        Return

      End Function f
    End Module d01ahfe_mod
    Program d01ahfe

!     D01AHF Example Main Program

!     .. Use Statements ..
      Use d01ahfe_mod, Only: f, nin, nout
      Use nag_library, Only: d01ahf, nag_wp
!     .. Implicit None Statement ..
      Implicit None
!     .. Local Scalars ..
      Real (Kind=nag_wp)               :: a, ans, b, epsr, relerr
      Integer                          :: ifail, nlimit, npts
!     .. Executable Statements ..
      Write (nout,*) 'D01AHF Example Program Results'

      Read (nin,*)
      Read (nin,*) a, b
      Read (nin,*) nlimit
      Read (nin,*) epsr

      ifail = -1
      ans = d01ahf(a,b,epsr,npts,relerr,f,nlimit,ifail)

      Select Case (ifail)
      Case (0:2)
        Write (nout,*)
        Write (nout,99999) 'Integral = ', ans
        Write (nout,*)
        Write (nout,99998) 'Estimated relative error = ', relerr
        Write (nout,*)
        Write (nout,99997) 'Number of function evaluations = ', npts
      End Select

99999 Format (1X,A,F8.5)
99998 Format (1X,A,E10.2)
99997 Format (1X,A,I5)
    End Program d01ahfe