Dirk Thierbach wrote:

>>>Pass the stack as an argument to those functions that need it.
> 
> 
>>Precisely this is how you would have to do this with ML. But then, if
>>you do not just deal with one stack, but have more complicated context,
>>OR if you have to start thinking about threading the stack through
>>functions that do not use it, but use other functions which use it,
>>things easily get quite awkward.
> 
> 
> So could one "hide the plumbing" in a monad?

Hmmm. In principle, yes. I think that should be possible here.
(Done this for a related problem where contextual typesetting
information is passed around.)

-- 
best regards,
Thomas Fischbacher
tf@functionality.de