program main

!*****************************************************************************80
!
!! recursive_sub_test() demonstrates the use of recursive subroutines.
!
!  Licensing:
!
!    This code is distributed under the MIT license.
!
!  Modified:
!
!    08 June 2007
!
!  Author:
!
!    John Burkardt
!
  implicit none

  integer, parameter :: n = 10

  integer n_copy
  integer i4vec(n)

  call timestamp ( )

  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) 'RECURSIVE_SUB_TEST():'
  write ( *, '(a)' ) '  FORTRAN90 version.'
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) '  Demonstrate recursive subroutine definitions.'
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) '  We sort a vector by recursion.'
  write ( *, '(a)' ) '  Our recursive step finds the largest element and moves'
  write ( *, '(a)' ) '  it to the end.'

  call i4vec_uniform_ab ( n, 0, 10, i4vec )

  call i4vec_print ( n, i4vec, '  Unsorted vector:' )

  n_copy = n

  if ( 1 < n ) then
    call i4vec_max_back ( n_copy, i4vec )
  end if

  call i4vec_print ( n, i4vec, '  Sorted vector:' )
!
!  Terminate.
!
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) 'RECURSIVE_SUB_TEST:'
  write ( *, '(a)' ) '  Normal end of execution.'

  write ( *, '(a)' ) ' '
  call timestamp ( )

  stop
end
recursive subroutine i4vec_max_back ( n, i4vec )

!*****************************************************************************80
!
!! I4VEC_MAX_BACK sorts a vector recursively.
!
!  Discussion:
!
!    On each call, this subroutine finds the maximum entry in the
!    vector, moves it to position N, reduces N by 1, and calls itself
!    again.
!
!  Licensing:
!
!    This code is distributed under the MIT license.
!
!  Modified:
!
!    27 November 2006
!
!  Author:
!
!    John Burkardt
!
!  Parameters:
!
!    Input, integer N, the size of the input vector.
!
!    Input/output, integer I4VEC(N), the vector being sorted.
!
  implicit none

  integer n

  integer big
  integer i4vec(n)
  integer loc(1)
!
!  Find maximum, move to the end.
!
  if ( 2 <= n ) then
    loc = maxloc ( i4vec(1:n) )
    big = i4vec(loc(1))
    i4vec(loc(1):n-1) = i4vec(loc(1)+1:n)
    i4vec(n) = big
  end if
!
!  Sort the vector of length N-1.
!
  if ( 3 <= n ) then
    call i4vec_max_back ( n-1, i4vec )
  end if

  return
end
subroutine i4vec_print ( n, a, title )

!*****************************************************************************80
!
!! I4VEC_PRINT prints an I4VEC.
!
!  Discussion:
!
!    An I4VEC is a vector of integer values.
!
!  Licensing:
!
!    This code is distributed under the MIT license.
!
!  Modified:
!
!    28 November 2000
!
!  Author:
!
!    John Burkardt
!
!  Parameters:
!
!    Input, integer N, the number of components of the vector.
!
!    Input, integer A(N), the vector to be printed.
!
!    Input, character ( len = * ) TITLE, a title to be printed first.
!    TITLE may be blank.
!
  implicit none

  integer n

  integer a(n)
  integer i
  character ( len = * ) title

  if ( 0 < len_trim ( title ) ) then
    write ( *, '(a)' ) ' '
    write ( *, '(a)' ) trim ( title )
  end if

  write ( *, '(a)' ) ' '
  do i = 1, n
    write ( *, '(2x,i8,2x,i12)' ) i, a(i)
  end do

  return
end
subroutine i4vec_uniform_ab ( n, a, b, x )

!*****************************************************************************80
!
!! i4vec_uniform_ab() returns a scaled pseudorandom I4VEC.
!
!  Discussion:
!
!    An I4VEC is a vector of I4's.
!
!    The pseudorandom numbers should be scaled to be uniformly distributed
!    between A and B.
!
!  Licensing:
!
!    This code is distributed under the MIT license. 
!
!  Modified:
!
!    15 April 2025
!
!  Author:
!
!    John Burkardt
!
!  Input:
!
!    integer n: the dimension of the vector.
!
!    integer a, b: the limits of the interval.
!
!  Output:
!
!    integer x(n): a vector of numbers between A and B.
!
  implicit none

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

  integer n

  integer a
  integer b
  integer i
  real ( kind = rk ) r
  integer x(n)

  do i = 1, n
    call random_number ( harvest = r )
    x(i) = a + int ( ( b + 1 - a ) * r )
  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:
!
!    06 August 2005
!
!  Author:
!
!    John Burkardt
!
!  Parameters:
!
!    None
!
  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