Re: Array modification feature

[John G. Aspinall <JGA at MIT-MC>]

    From: DLA at MIT-AI (David L. Andre)

    A neat feature in arrays which would have been useful to me many times
    recently would be the ability to tell if any element of an array has
    been modified since some other time....

    The advantage of this arises in the following type of situation:

    (progn (unmodify-array foo)
           (do-something-which-might-modify foo)
           (if (modified-array foo)
    	   (make-consistent foo)))

I have a situation like this involving redisplay of graphic objects
if they have been changed by (do-something-which-might-modify foo).

However, I find nothing wrong with a stack onto which
do-something-which-might-modify pushes the array subscripts which have
been modified.  Unless the modification is so trivial that the stack push
adds a significant amount of effort to the modification function, this
seems like a way to do it without modify bits for every word.