recursive subroutine collatz_path ( n ) !*****************************************************************************80 ! !! COLLATZ_PATH uses recursion to print the path of a Collatz sequence. ! ! Licensing: ! ! This code is distributed under the MIT license. ! ! Modified: ! ! 09 March 2012 ! ! Author: ! ! John Burkardt ! ! Parameters: ! ! Input, integer N, the current member of the path. ! implicit none integer n write ( *, '(2x,i8)' ) n if ( n < 1 ) then write ( *, '(a)' ) ' ' write ( *, '(a)' ) 'COLLATZ_PATH - Fatal error!' write ( *, '(a,i8,a)' ) ' Path member N = ', n, ' is not positive.' stop else if ( n == 1 ) then else if ( mod ( n, 2 ) == 0 ) then call collatz_path ( n / 2 ) else call collatz_path ( 3 * n + 1 ) end if 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 ! 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