NAG Library Manual, Mark 28.4
!   E04ABF Example Program Text
!   Mark 28.4 Release. NAG Copyright 2022.
Module e04abfe_mod

!     E04ABF 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                           :: funct
!     .. Parameters ..
Integer, Parameter, Public       :: nout = 6
Contains
Subroutine funct(xc,fc)
!       Routine to evaluate F(x) at any point in (A, B)

!       .. Scalar Arguments ..
Real (Kind=nag_wp), Intent (Out) :: fc
Real (Kind=nag_wp), Intent (In) :: xc
!       .. Intrinsic Procedures ..
Intrinsic                      :: sin
!       .. Executable Statements ..
fc = sin(xc)/xc

Return

End Subroutine funct
End Module e04abfe_mod
Program e04abfe

!     E04ABF Example Main Program

!     .. Use Statements ..
Use e04abfe_mod, Only: funct, nout
Use nag_library, Only: e04abf, nag_wp
!     .. Implicit None Statement ..
Implicit None
!     .. Local Scalars ..
Real (Kind=nag_wp)               :: a, b, e1, e2, f, x
Integer                          :: ifail, maxcal
!     .. Executable Statements ..
Write (nout,*) 'E04ABF Example Program Results'

!     E1 and E2 are set to zero so that E04ABF will reset them to
!     their default values

e1 = 0.0_nag_wp
e2 = 0.0_nag_wp

!     The minimum is known to lie in the range (3.5, 5.0)

a = 3.5_nag_wp
b = 5.0_nag_wp

!     Allow 30 calls of FUNCT

maxcal = 30

ifail = -1
Call e04abf(funct,e1,e2,a,b,maxcal,x,f,ifail)

Select Case (ifail)
Case (0,2)
Write (nout,*)
Write (nout,99999) 'The minimum lies in the interval', a, ' to', b
Write (nout,99999) 'Its estimated position is', x, ','
Write (nout,99998) 'where the function value is ', f
Write (nout,99997) maxcal, 'function evaluations were required'
End Select

99999 Format (1X,A,F11.8,A,F11.8)
99998 Format (1X,A,F7.4)
99997 Format (1X,I2,1X,A)
End Program e04abfe