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From: frechett@spot.Colorado.EDU (-=Runaway Daemon=-)
Newsgroups: comp.sys.handhelds
Subject: Re: CLEARing stack
Keywords: CLEAR
Message-ID: <1991Jan29.044750.1789@csn.org>
Date: 29 Jan 91 04:47:50 GMT
References: <10535@jarthur.Claremont.EDU>
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Organization: University of Colorado, Boulder
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In article <10535@jarthur.Claremont.EDU> sburke@jarthur.Claremont.EDU (Scott Burke) writes:
>Here are some more thoughts on stack clearing.
>hit on the solution I have found to work acceptably:  to use a stack depth
>counter and then upon exiting the program, restore the correct depth of the
>stack.  This simply changes the headache, however, because now the code has
Ummm excuse me if this sounds too simple but why do you need a stack counter 
that keeps track of additions and subtractions from the stack.?

>Scott.
>sburke@jarthur.claremont.edu

Let me work this out.  If start the program with DEPTH -> STKdpth
at ANY point in the program, I could kill everything but that original stuff
with a routine like this.. Here is a sample program that I just tried out.
\<< DEPTH \-> STKdpth 
  \<< HALT
DEPTH STKdpth DROPN 
  \>>
\>>

When executed it stops at HALT.. I can do anything that I damn well please to
the stack short of killing the original stuff that was on the stack.. 
for my test I had.
4:         4
3:         3
2:         2
1:         1
and when it halted, I entered as much crap as I could stand to add to the
stack.  Performed Calculations etc.. 
then hit CONT and poof the only thing left on the stack was.
4:         4
3:         3
2:         2
1:         1

I can't think of ANYTHING simpler than this..
If you have a program that tends to devour stuff that was previously on the 
stack then I pity your program.. 
If it is supposed to eat some arguments then it is a simple matter to subtract
1 or 2 from STKdpth.  

I just am not sure what you meant by having all this keeping track of stack
stuff.  Take the example you gave of EDIT and the ^STK function. Let's say I 
was going to write EDIT with my routines... I might define the ^STK function as
something like 
\<< DEPTH STKdpth ->LIST          @puts any current program stuff in a list.  
    -> Temp.shit                  @Put list in local Var.  Who cares if it dies.
    LOOKATSTACK_ROUTINE           @the catalog like thing that ^STK does.
Temp.shit LIST-> ROLL             @Bet we will deal with ECHOed stuff next.
\>>

Give me an example where this wouldn't screw up other than HUNGRY programs
or of course ones that use CLEAR.. ;)

	ian
--

-=Runaway Daemon=-