program main

!*****************************************************************************80
!
!! besselzero_test() tests besselzero().
!
!  Licensing:
!
!    This code is distributed under the MIT license.
!
!  Modified:
!
!    06 June 2025
!
!  Author:
!
!    John Burkardt
!
  call timestamp ( )

  write ( *, '(a)' ) ''
  write ( *, '(a)' ) 'besselzero_test():'
  write ( *, '(a)' ) '  Fortran90 version'
  write ( *, '(a)' ) '  Test besselzero()'

  call besselzero_j_print ( )
  call besselzero_y_print ( )
!
!  Terminate.
!
  write ( *, '(a)' ) ''
  write ( *, '(a)' ) 'besselzero_test():'
  write ( *, '(a)' ) '  Normal end of execution.'
  call timestamp ( )

  return
end
subroutine besselzero_j_print ( )

!*****************************************************************************80
!
!! besselzero_j_print() tests jn_zeros() for the Bessel J function.
!
!  Licensing:
!
!    This code is distributed under the MIT license.
!
!  Modified:
!
!    08 June 2025
!
!  Author:
!
!    John Burkardt
!
  implicit none

  integer, parameter :: rk8 = kind ( 1.0D+00 )

  integer, parameter :: nt = 10

  integer i
  integer n
  real ( kind = rk8 ) z0(nt)
  real ( kind = rk8 ) z1(nt)

  write ( *, '(a)' ) ''
  write ( *, '(a)' ) 'besselzero_j_print():'
  write ( *, '(a)' ) '  Print zeros of Bessel j function.'

  n = 0
  call jn_zeros ( n, nt, z0 )

  n = 1
  call jn_zeros ( n, nt, z1 )

  write ( *, '(a)' ) ''
  write ( *, '(a)' ) '    i    J0(root i)  J1(root i)'
  write ( *, '(a)' ) ''
  do i = 1, nt
    write ( *, '(2x,i2,2x,g14.6,x,g14.6)' ) i, z0(i), z1(i)
  end do

  return
end
subroutine besselzero_y_print ( )

!*****************************************************************************80
!
!! besselzero_y_print() tests besselzero() for the Bessel Y function.
!
!  Licensing:
!
!    This code is distributed under the MIT license.
!
!  Modified:
!
!    08 June 2025
!
!  Author:
!
!    John Burkardt
!
  implicit none

  integer, parameter :: rk8 = kind ( 1.0D+00 )

  integer, parameter :: nt = 10

  integer i
  integer n
  real ( kind = rk8 ) z0(nt)
  real ( kind = rk8 ) z1(nt)

  write ( *, '(a)' ) ''
  write ( *, '(a)' ) 'besselzero_y_print():'
  write ( *, '(a)' ) '  Print zeros of Bessel y function.'

  n = 0
  call yn_zeros ( n, nt, z0 )

  n = 1
  call yn_zeros ( n, nt, z1 )

  write ( *, '(a)' ) ''
  write ( *, '(a)' ) '    i    Y0(root i)  Y1(root i)'
  write ( *, '(a)' ) ''
  do i = 1, nt
    write ( *, '(2x,i2,2x,g14.6,x,g14.6)' ) i, z0(i), z1(i)
  end do

  return
end
subroutine timestamp ( )

!*****************************************************************************80
!
!! timestamp() prints the current YMDHMS date as a time stamp.
!
!  Example:
!
!    31 May 2001   9:45:54.872 AM
!
!  Licensing:
!
!    This code is distributed under the MIT license.
!
!  Modified:
!
!    15 August 2021
!
!  Author:
!
!    John Burkardt
!
  implicit none

  character ( len = 8 ) ampm
  integer d
  integer h
  integer m
  integer mm
  character ( len = 9 ), parameter, dimension(12) :: month = (/ &
    'January  ', 'February ', 'March    ', 'April    ', &
    'May      ', 'June     ', 'July     ', 'August   ', &
    'September', 'October  ', 'November ', 'December ' /)
  integer n
  integer s
  integer values(8)
  integer y

  call date_and_time ( values = values )

  y = values(1)
  m = values(2)
  d = values(3)
  h = values(5)
  n = values(6)
  s = values(7)
  mm = values(8)

  if ( h < 12 ) then
    ampm = 'AM'
  else if ( h == 12 ) then
    if ( n == 0 .and. s == 0 ) then
      ampm = 'Noon'
    else
      ampm = 'PM'
    end if
  else
    h = h - 12
    if ( h < 12 ) then
      ampm = 'PM'
    else if ( h == 12 ) then
      if ( n == 0 .and. s == 0 ) then
        ampm = 'Midnight'
      else
        ampm = 'AM'
      end if
    end if
  end if

  write ( *, '(i2.2,1x,a,1x,i4,2x,i2,a1,i2.2,a1,i2.2,a1,i3.3,1x,a)' ) &
    d, trim ( month(m) ), y, h, ':', n, ':', s, '.', mm, trim ( ampm )

  return
end