program main

!*****************************************************************************80
!
!! sncndn_test() tests sncndn().
!
!  Licensing:
!
!    This code is distributed under the MIT license.
!
!  Modified:
!
!    25 August 2020
!
!  Author:
!
!    John Burkardt
!
  call timestamp ( )
  write ( *, '(a)' ) ''
  write ( *, '(a)' ) 'sncndn_test():'
  write ( *, '(a)' ) '  Fortran90 version'
  write ( *, '(a)' ) '  Test sncndn(), to evaluate Jacobi elliptic functions.'

  call jacobi_cn_test ( )
  call jacobi_dn_test ( )
  call jacobi_sn_test ( )
!
!  Terminate.
!
  write ( *, '(a)' ) ''
  write ( *, '(a)' ) 'sncndn_test():'
  write ( *, '(a)' ) '  Normal end of execution.'
  call timestamp ( )

  stop 0
end
subroutine jacobi_cn_test ( )

!*****************************************************************************80
!
!! jacobi_cn_test() tests jacobi_cn().
!
!  Licensing:
!
!    This code is distributed under the MIT license.
!
!  Modified:
!
!    25 June 2018
!
!  Author:
!
!    John Burkardt
!
  implicit none

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

  real ( kind = rk8 ) cn1
  real ( kind = rk8 ) cn2
  real ( kind = rk8 ) jacobi_cn
  real ( kind = rk8 ) m
  integer n_data
  real ( kind = rk8 ) u

  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) 'jacobi_cn_test():'
  write ( *, '(a)' ) '  jacobi_cn() evaluates the Jacobi elliptic function CN.'
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) '    U       M       Exact CN                CN(U,M)'
  write ( *, '(a)' ) ' '

  n_data = 0

  do

    call jacobi_cn_values ( n_data, u, m, cn1 )

    if ( n_data == 0 ) then
      exit
    end if

    cn2 = jacobi_cn ( u, m )

    write ( *, '(2f8.4,2g24.16)' ) u, m, cn1, cn2

  end do

  return
end
subroutine jacobi_dn_test ( )

!*****************************************************************************80
!
!! jacobi_dn_test() tests jacobi_dn().
!
!  Licensing:
!
!    This code is distributed under the MIT license.
!
!  Modified:
!
!    25 June 2018
!
!  Author:
!
!    John Burkardt
!
  implicit none

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

  real ( kind = rk8 ) dn1
  real ( kind = rk8 ) dn2
  real ( kind = rk8 ) jacobi_dn
  real ( kind = rk8 ) m
  integer n_data
  real ( kind = rk8 ) u

  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) 'jacobi_dn_test():'
  write ( *, '(a)' ) '  jacobi_dn() evaluates the Jacobi elliptic function DN.'
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) '    U       M       Exact DN                DN(U,M)'
  write ( *, '(a)' ) ' '

  n_data = 0

  do

    call jacobi_dn_values ( n_data, u, m, dn1 )

    if ( n_data == 0 ) then
      exit
    end if

    dn2 = jacobi_dn ( u, m )

    write ( *, '(2f8.4,2g24.16)' ) u, m, dn1, dn2

  end do

  return
end
subroutine jacobi_sn_test ( )

!*****************************************************************************80
!
!! jacobi_sn_test() tests jacobi_sn().
!
!  Licensing:
!
!    This code is distributed under the MIT license.
!
!  Modified:
!
!    25 June 2018
!
!  Author:
!
!    John Burkardt
!
  implicit none

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

  real ( kind = rk8 ) m
  real ( kind = rk8 ) jacobi_sn
  integer n_data
  real ( kind = rk8 ) sn1
  real ( kind = rk8 ) sn2
  real ( kind = rk8 ) u

  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) 'jacobi_sn_test():'
  write ( *, '(a)' ) '  jacobi_sn() evaluates the Jacobi elliptic function SN.'
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) '    U       M       Exact SN                SN(U,M)'
  write ( *, '(a)' ) ' '

  n_data = 0

  do

    call jacobi_sn_values ( n_data, u, m, sn1 )

    if ( n_data == 0 ) then
      exit
    end if

    sn2 = jacobi_sn ( u, m )

    write ( *, '(2f8.4,2g24.16)' ) u, m, sn1, sn2

  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:
!
!    18 May 2013
!
!  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