perm filename BAIL.UPD[DOC,AIL] blob sn#206175 filedate 1976-03-13 generic text, type C, neo UTF8
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C00002 00002	Changes since original printing of BAIL manual AIM-270
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Changes since original printing of BAIL manual AIM-270
		BAIL ver. 12-Mar-76

Locations specified to BREAK  using block names may now  use only "."
(period) for the delimiter; e.g., BREAK("block.proc");.

Returns the coordinate number of the location  given as its argument.
LOCATION has the same syntax as in BREAK.

PROCEDURE DEFINE(char,"macro");
Macros from  the source  file(s) are  not recognized  at the  present
time.   There  are 26  character macros definable,  from "A"  to "Z".
DEFINE macros  substitute the  given string  for  each occurrance  of
<alt><char> which is not part of a string constant.  If the operating
system can send characters of more than 7 bits to INCHWL (INTTY under
TENEX) then any activation  character with high order bits  will also
activate the macro.  Thus  at Stanford <alt>P, αP, and αβP are all
equivalent.  In all  cases the character is  converted to upper  case
before doing anything else.  The macros G, P, S, and X are predefined
to be " !!GO;", " !!GO;", " !!STEP;", and " !!GSTEP;" respectively.

Variables not  in the current  scope can be  referenced by  using the
same  scheme  used to  describe  locations  to BREAK.    If  you have
something of your own  named SHOW then you  can access the BAIL  SHOW
function  by using  $RUN$.SHOW(coord);.   Warning: this  mode assumes
that you know what you are doing.

When BAIL  is loaded  by a non-TENEX  system, it  sets .JBDDT to  the
address  of one of  its routines. (The  routine is B.  referred to in
AIM-270. If you load both BAIL  and DDT, then the last module  loaded
wins.) Under  TENEX, BAIL sets  .JBDDT only if  it is zero  when BAIL

pseudoPROCEDURE !!GOTO("location");
The return address is set to the location  specified, and then a !!GO
is done.  Note  that the location should be in the same lexical scope
as the most recent  entry to BAIL, or  the program will probably  get

pseudoPROCEDURE !!UP(level);
This procedure trims the  runtime stack back to level,  then reenters
BAIL.   CLEANUPs and  deallocations are performed  for the procedures
thus killed.  Level has the same interpretation as in SETLEX,  and in
addition must not designate a SIMPLE procedure.  Suppose you ask BAIL
to  evaluate a procedure call,  the procedure hits  an error, and you
want to get back to  where you were before the procedure  was called.
Then !!UP will do the trick if the value of level is correct.

INTERNAL STRING !!QUERY; [Declare as EXTERNAL in your program.]
Whenever BAIL wants input, it checks this string first.  If it is not
NULL, then !!QUERY is used instead of asking the operating system for
input from the terminal.  (!!QUERY  is set to NULL each time this  is
done.) Thus  a program can simulate  the effect of typing  to its own
input buffer  by stuffing the text into !!QUERY.  In particular, file
input to  BAIL  and various  macro  hacks can  be effected  by  using
procedures which assign values to !!QUERY.

If you have processes,  then SETSCOPE can be used to  peek around the
world.  Specifically,  the static and dynamic scopes are set to those
of the process for which PITEM is the process item.  This  will allow
access  to  variables and  traceback  from  TEXT,  but care  must  be
exercised  when calling procedures.   A call to  a procedure which is
not defined at the  top level will probably  not work.  Also,  if the
procedure  does not  return  successfully then  your  stacks will  be
hopelessly confused.

Note on processes: BAIL  runs in the process which  caused the break.
Thus  stack space  must be  provided  in each  process.   The minimum
amount is PSTACK(4)+STRINGSTACK(2).

BAIL and  other language  processors: If  procedures are compiled  by
some processor  other than SAIL (e.g.   FAIL, MACRO, BLISS, ...) then
further steps must be taken if BAIL is to know about them.  BAIL must
have access to a procedure descriptor  in order to call any procedure
(cf.   the  /4B  switch).   Thus a  user who  wishes to  use assembly
language procedures  with  BAIL  must provide  appropriate  procedure
descriptors.   The file SAILPD.FAI[S,AIL] defines a  FAIL macro which
will generate a SAIL procedure descriptor.  The procedure descriptors
may reside in a separate load module if desired;  but they must be in
the core image when BAIL is being used.