COMMENT ⊗   VALID 00003 PAGES
C REC  PAGE   DESCRIPTION
C00001 00001
C00002 00002	.NEWSEC USER FEATURES, PROGRAM FORMULATION
C00012 00003	.DIA: NEWSEC EXAMPLE DIALOG WITH THE HAL SYSTEM, SAMPLE DIALOG
C00021 ENDMK
C⊗;
.NEWSEC USER FEATURES, PROGRAM FORMULATION

	The HAL  system is  intended to  be a  flexible tool for  the
planning  of  complex  assembly tasks  by  a  skilled operator.  This
planning has  several  phases: initial  preparation of  the  program,
removing syntactic errors  from the source code,   trying the program
out,   and   fixing   discovered   bugs   until   the   program   works
properly.   The  final  stage is  the  production run  of  the
program,  which can occur  in a  basically unsupervised  mode. During
execution, however, it is still possible to interrupt the machine and
find out exactly where it  is in the plan and debug  it further. This
is  useful for  patching a program  which over  the course of  a long
execution begins to "drift" from reality.
	Thus, the  user features can  be divided  roughly into  these
parts:

.NEWSS	PROGRAM FORMULATION

	It is  hoped that the  HAL language described in  some detail
earlier  provides a  clear and  complete system  in which  to express
those  manipulations  necessary  for  the  correct  execution  of  an
assembly task.  The structured concept of statement, made powerful by
the relatively unstructured  concept of the  on-monitor, should  make
writing in HAL relatively easy.  
	One other way in which HAL can  assist the programmer is that
she can  have it read the current location of  an arm and to use that
frame as a constant in her program.  This makes programming  by doing
possible.  One way to put together a simple program is merely to move
the arm  manually to the different locations desired, have the system
remember  those  locations,  and  then  type  in  appropriate  motion
commands between these points.

.NEWSS	PROGRAM COMPILATION

	The supervisor is the key to this and the following features;
it  allows the user  to oversee the  progress of her  program and fix
errors as  they  arise.   There  is  a simple  "supervisor  language"
intended for communication with the HAL system.  Some of its commands
are  demonstrated in  the sample  dialog given  in {secref dia}.  One  of the
commands causes compilation to begin; the parser is  directed to read
some file.  An  option  is to have console input itself used to enter
the source code; this is especially  useful in causing the arm to  do
something immediately. When the parser finds a  syntax error, it will
give  an  error  message, and  several  options  will  in general  be
available.  These include  aborting the compilation, skipping to  the
end of the  current statement, editing the line with  the system line
editor  (after  which  the  entire  statement  will  be reparsed,  if
possible), and  temporarily switching  to a  text editor  to fix  the
problem (after which the entire program must be reparsed).  
	The expander can also find errors; these are usually semantic
errors, like generating  a move  to a point  with undefined  planning
value, not supplying enough information to a high-level primitive, or
attempting to move the same arm simultaneously in two blocks of code.
In those cases where the problem is one of  insufficient information,
the expander will  prompt for more, and, if possible,  continue.  The
user may decide not to supply that information, and in that case, the
offending statement is  flushed.   Some errors are  so drastic as  to
require complete  recompilation; the user is always  given the option
of switching to a text editor for major modifications.
	There is  a limited  number of  errors which  the  trajectory
calculator is capable  of discovering.  These mostly  involve motions
beyond the  capability of the manipulators involved.   Options to the
user include making the  best legal trajectory possible, causing  the
trajectory to be slowed down, and putting in a null trajectory.

.NEWSS	PROGRAM EXECUTION

	After a  program has been compiled,  it resides on disk  as a
load module.   Any number of load modules can be loaded together; the
principal restriction is that each of them be a  "top level" program.
As mentioned earlier, the loader will resolve calls between the large
(planning) computer  and the  small  (execution) computer  for  those
functions  which  the  user has  decided  require  the  computational
ability found only on the large computer.
	Execution  is initiated by another  supervisor command issued
by the user.  While the  mini is executing the program, the user  can
cause an interruption  and examine values within  the runtime system,
and  modify them if she  wishes.  It is also  possible to examine the
code generated by the compiler and modify it, but this is most likely
only  of interest to  system programmers.   Sizable  patches require
recompilation.
	Sometimes hardware difficulties will cause abrupt termination
of  the   program;  these  often   are  due  to   runtime  trajectory
modifications  overstraining the  hardware.   After issuing  an error
message to the user,  the system behaves just  as it would should  it
have been interrupted manually.
	It is possible, during one of these "breaks", to request that
the  entire world  be saved.   This causes  all runtime  values to be
written out  into a  safe place,  along with  the current  attachment
structure and  the current program counters.   There are several uses
for this  feature:  it allows  the  debugging  of the  task  to  stop
temporarily and  to be resumed  later.  More  important, it  plants a
"safe point" in the  code, so that if an error should occur later, it
is possible to back up the program to a point at which everything was
still working.
	Programs  which   have  been   completely  debugged   can  be
"unloaded",  that is, saved in a dump  file for execution any time in
the future.
.DIA: NEWSEC EXAMPLE DIALOG WITH THE HAL SYSTEM, SAMPLE DIALOG


	Here is a sample conversation a user  might have with HAL. It
demonstrates the  following features: Typing in  source code by hand,
requesting source code to be  read from a file,  immediate  execution
of  commands by  the  arm, return  of values  from  the arm,  loading
compiled code into the runtime computer, and executing that code.
	The supervisor prompts with the sign "⊃".  The material in
the right-hand column is explanatory.
.BEGIN
.COMMAND CHARACTER "~";
~NOFILL; NOJUST;TURN OFF "←";

%7
⊃ COMPILE TTY				| Request to read in from
					| console for compilation.
⊂ type <alt> when done ⊃		| Message from supervisor
MOVE YELLOW				| Simple move statement
        TO [(20 30 1):(π 0 0)];		| Destination
FRAME PLACE1;				| Declaration
PLACE1 ← YELLOW;			| Assignment
PLACE2 ← PLACE1+(0 0 5);		| Assignment
⊂ OK to declare PLACE2 a FRAME? ⊃  YES	| Parser error, with option.
$					| End of file (altmode)
⊂ no errors. compiled:  TTY(1) ⊃	| Compiler message.  
⊃ IMMEDIATE				| Request for an immediate
					|   action
⊂ type <alt> when done ⊃		| Message from supervisor
MOVE YELLOW TO PARK  $			| User wants to park the arm
⊂ done ⊃				| And does
⊃ EXECUTE				| Request to execute compiled
					|   code
⊂ loading TTY(1) ⊃			| First, loading to be done
⊂ executing TTY(1) ⊃			| Message as execution starts
⊂ done ⊃				| Message at end of execution
⊃ READ PLACE3 ← YELLOW			| Ask to read hand position
⊂ OK to declare PLACE3 a FRAME? ⊃  YES  | Use of undeclared variable
⊂ PLACE3 = [(19.9, 30.1, 1.1):(3.1, 0, 0.1)] ⊃	
					| Indication of what was set
⊃ VALUE PLACE4				| Ask for value of variable
⊂ PLACE4 not declared. Declare it a ⊃ 	| User has chance to fix
⊂ Please retype command ⊃ 		|   simple errors.
⊃ PLANVALUE V1				| Request for planning value
⊂  (V1) = (3.0, 0, 20.13) ⊃		|
⊃ PLANVALUE V1 ← (4.0, 0, 20.13)	| User can change planvalues.
⊃ VALUE V1 ← (4.0, 0, 20.13)		| User can change real values.
⊃ COMPILE HACK.HAL[1,LOU]		| Ask for compile from file
⊂ Error in line 310 of HACK.HAL[1,LOU].	| Parser error message
                        THEN 		| Gives line with <lf>
                             STUP	|   at point of error
Option ⊃ ?				| User typed "?"
I:	Insert replacement text		| A list of options to user
Z:	Use line editor to fix		|
M:	Show more context		| This would give entire
F:	Flush to end of statement	|   statement
E:	Switch to E			| E is a text editor
S:	Switch to SOS			| SOS is a text editor
Q:	Quit. Abort compilation		|
Option ⊃ I				| User chooses to insert
					|   replacement
⊂ type <alt> when done ⊃		| Message from supervisor
                        THEN STOP	|  "STUP" changed to "STOP"
$					| End of insertion
⊂ error in line 520 of HACK.HAL[1,LOU]. | trajectory calculator error
					|   message
        MOVE YELLOW 			| Only first line of
					|   statement given
The desired motion goes out of bounds in joint 3
in the first segment of motion.		|
					| A bad motion
Option ⊃ E				| User wants to edit with E.
⊂ Switching to E.  To return, <CTR>XG<CR> ⊃
					| Universe is saved for retry
⊂ Welcome back to HAL. 			| Editing done
Compilation of HACK.HAL[1,LOU] aborted⊃	| After an edit, compilation
					|   aborts.
⊃ COMPILE HACK.HAL[1,LOU]		| Request for recompilation
⊂ No errors. Compiled: TTY(1), HACK.HAL[1,LOU] ⊃
					| Compilation succeeds.  
⊃ LOAD					| Request to load into servo
⊂ Loaded:  TTY(1), HACK.HAL[1,LOU] ⊃	|
⊃ STATUS				| User wants to know where
					|   she is
BLUE at [(19.9, 30.1, 1.1) : (3.1, 0, 0.1)]
					| Arm location
Compiled: TTY(1), HACK.HAL[1,LOU]	| Compilation status
Loaded: TTY(1), HACK.HAL[1,LOU]		| Runtime status
⊃ EXECUTE				| Request for execution
⊂ Executing TTY(1), HACK.HAL[1,LOU] ⊃	|
⊃ STATUS				| User wants to know where
					|   she is
BLUE at [(24.1, 30.1, 5.3) : (3.1, 0, 0)] moving
					| Arm status
Interpreter at line 320 in HACK.HAL[1,LOU]
					| Servo status
⊂ Interrupted by red button⊃		| Runtime error message. User
					|   interrupted motion.
Interpreter at line 180 of HACK.HAL[1,LOU]
					| Servo status
⊃ PROCEED				| Request to continue motion
⊂ Joint 4 has excessive force.		| Runtime error message.
Interpreter at line 150 of HACK.HAL[1,LOU]
					| Servo status
⊃ DELETE 1				| Request to delete last
					|   compilation
⊂ Deleting HACK.HAL from runtime	| Removed from runtime
⊂ Deleting HACK.HAL from COMPILATION	| Removed from world of
					|   compiler
⊃ E					| Switch to E.
⊂ Switching to E.  To return, <CTR>XG<CR>⊃
⊂ Welcome back to HAL⊃			|
⊃ COMPILE HACK.HAL[1,LOU]		| Request for compilation
⊂ No errors. Compiled: TTY(1), HACK.HAL[1,LOU] ⊃
					| Compilation succeeds
⊃ SAVE WORLD IN W1			| User wants world saved in
⊂ World saved in W1.WLD ⊃		|   named location.
⊃ RESTORE WORLD FROM W0			| Request to restore previous
					|   world
⊂ W0.WLD not found ⊃			| Expander error message
⊃ RESTORE WORLD FROM W00		| Request to restore previous
					|   world
⊂ done 					|
Note:  TTY(1), HACK.HAL[1,LOU] still compiled. ⊃
					| This is done, but previous
					|   stuff is still around.
⊃ BYE					| Request to leave the room.
⊂ Final status:				| A final status rundown
Load modules ready:  TTY(1).HLD, HACK.HLD
BLUE at [(19.9, 30.1, 1.1) : (3.1, 0, 0.1)]
Goodbye ⊃
EXIT
.%*
~ COMMAND CHARACTER ".";
.END