TF syntax checking
------------------
O-Plan be run as a TF syntax-checker ("tfc").  This can be useful
when writing a new domain description.  O-Plan performs the same
checks when a TF file is loaded, but it's sometimes easier if you 
can check without starting up the whole planner.  "tfc" also lets 
you ask for a level analysis to be printed which normally happens 
only when there are level errors.

O-Plan will run as the syntax-checker if it's given "-tfc" as a
command-line argument.  Arguments after "-tfc" are interpreted by 
the syntax-checker.  They can take the following forms:

   [-q] [-l [-e]] filename
   [-q] [-l [-e]] -d directory

where the square brackets surround optional items.  At present, the
items must appear in the order given.

"-q" is for "quiet" and suppresses progress reports. 
"-l" is for "levels" and produces a level analysis.
"-e" can be used with "-l" to have the level analysis list the
     effect names for each action (to make it easier to see where
     the effect-levels come from).  This does not include the
     effects of subactions.

When "-d" is used, all files in the directory are checked and
a report is produced at the end.

If the filename is the single character "-", TF forms will be read
from standard-input.  Progress reports will be turned off
automatically.

If no additional arguments are supplied after "-tfc", the checker
enters a loop in which you can type tfc commands.  E.g

   shell% oplan -tfc
   tfc> -q -l snark.tf
   tfc>

To exit, type "q" (not "-q") as a command.

Here is an example of a level analysis:

   shell% oplan -tfc -q -l demo/tf/pacifica-1

   Levels for domain "pacifica-1"

   There are 0 strongly connected components in the
   action graph that have length greater than one.

   Action levels:
      0 task_operation_castaway
	task_operation_paradise
	task_operation_blue_lagoon
      1 fly_passengers
	transport
	fly_transport
      2 load
	unload
	drive

   Effect levels:
      0 country
      1 nationals
	people_at_poe_from
      2 in_use_for
	at