program main

!*****************************************************************************80
!
!! disk_rule_test() tests disk_rule().
!
!  Licensing:
!
!    This code is distributed under the MIT license.
!
!  Modified:
!
!    18 April 2016
!
!  Author:
!
!    John Burkardt
!
  implicit none

  call timestamp ( )
  write ( *, '(a)' ) ''
  write ( *, '(a)' ) 'disk_rule_test():'
  write ( *, '(a)' ) '  FORTRAN90 version'
  write ( *, '(a)' ) '  Test disk_rule().'

  call test01 ( )
!
!  Terminate.
!
  write ( *, '(a)' ) ''
  write ( *, '(a)' ) 'DISK_RULE_TEST():'
  write ( *, '(a)' ) '  Normal end of execution.'
  write ( *, '(a)' ) ''
  call timestamp ( )

  stop 0
end
subroutine test01 ( )

!*****************************************************************************80
!
!! TEST01 tests DISK_RULE.
!
!  Licensing:
!
!    This code is distributed under the MIT license.
!
!  Modified:
!
!    18 April 2016
!
!  Author:
!
!    John Burkardt
!
  implicit none

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

  integer, parameter :: nr = 4
  integer, parameter :: nt = 8

  real ( kind = rk ) area
  integer d
  integer e(2)
  integer e1
  integer e2
  real ( kind = rk ) :: exact(15) = (/ &
       9.0D+00, &
       9.0D+00,            18.0D+00, &
     117.0D+00 / 4.0D+00,  18.0D+00,            225.0D+00 / 4.0D+00, &
     279.0D+00 / 4.0D+00, 117.0D+00 / 2.0D+00,  225.0D+00 / 4.0D+00, 387.0D+00 / 2.0D+00, &
    1773.0D+00 / 8.0D+00, 279.0D+00 / 2.0D+00, 1341.0D+00 / 8.0D+00, 387.0D+00 / 2.0D+00, 5769.0D+00 / 8.0D+00 /)
  integer i
  integer j
  integer k
  real ( kind = rk ) q
  real ( kind = rk ), parameter :: r8_pi = 3.141592653589793D+00
  real ( kind = rk ) rc
  real ( kind = rk ) s
  real ( kind = rk ) w(nr,nt)
  real ( kind = rk ) x(nr,nt)
  real ( kind = rk ) xc
  real ( kind = rk ) y(nr,nt)
  real ( kind = rk ) yc

  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) 'TEST01'
  write ( *, '(a)' ) '  DISK_RULE can compute a rule Q(f) for a general disk'
  write ( *, '(a)' ) '  with center (XC,YC) and radius RC,'
  write ( *, '(a)' ) '  using NT equally spaced angles and NR radial distances.'
  write ( *, '(a)' ) ''
  write ( *, '(a,i4)' ) '  NT = ', nt
  write ( *, '(a,i4)' ) '  NR = ', nr
  write ( *, '(a)' ) ''
  write ( *, '(a)' ) '  Estimate integrals I(f) where f = x^e(1) * y^e(2).'
!
!  Define the general disk.
!
  xc = 1.0D+00
  yc = 2.0D+00
  rc = 3.0D+00
!
!  Put in the factor of PI in the exact values.
!
  exact(1:15) = exact(1:15) * r8_pi
!
!  Compute the quadrature rule.
!
  call disk_rule ( nr, nt, xc, yc, rc, w, x, y )
!
!  Apply it to integrands.
!
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) '  E(1)  E(2)    I(f)            Q(f)' 
  write ( *, '(a)' ) ' '
!
!  Specify a monomial.
!
  k = 0

  do d = 0, 4

    do e1 = d, 0, -1

      e2 = d - e1
      e(1) = e1
      e(2) = e2

      s = 0.0D+00
      do j = 1, nt
        do i = 1, nr
          s = s + w(i,j) * x(i,j) ** e(1) * y(i,j) ** e(2)
        end do
      end do

      area = r8_pi * rc * rc
      q = area * s

      call disk01_monomial_integral ( e, exact )

      k = k + 1
      write ( *, '(3x,i2,3x,i2,2x,g14.6,2x,g14.6)' ) e(1), e(2), exact(k), q

    end do

  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 ( *, '(i2,1x,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