GET of a HUNK

[Kent M. Pitman <KMP at MIT-MC>]

    Date: 13 February 1981 20:03-EST
    From: Jon L White <JONL>

        Date: 12 February 1981 23:39-EST
        From: Richard L. Bryan <RLB at MIT-MC>

        How much cpu time have YOU wasted waiting for your program to run,
        when it turns out it was looping infinitely, doing GET off some extend?

    ...I ALWAYS SAID THAT HUNKS SHOULD PASS THE ATOM TEST!! SOOOO, I've just
    edited in the source the code for GET and GETL to distinguish between LIST
    non-atoms and HUNK non-atoms, and return () for the latter.

It REALLY bugs me that these things aren't discussed in advance. I don't
like this change and I would like it retracted. It is bad for two reasons:

 (1) It can break code. I haven't had time to analyze my packages to see
     if it does, but I don't use USRHUNK at all -- I like just bare hunks
     and I have used them as CDR-able objects and as objects with plists on
     a number of occasions. I don't know if I currently have code that cares
     and haven't had time to look. Even if it doesn't break any code, it
     radically changes the way in which hunks must be viewed as a tool for
     implementation -- i think NOT for the better.

 (2) It is not uniform with the treatment of non-user-hunks and the value of
     HUNKP elsewhere in Lisp. Please do not make changes to the language 
     which are not coherent with what little overall design philosophy there
     is still persisting in Maclisp after all the other changes that have
     been forced upon it to get NIL going.

The correct fix would have been to make only USRHUNKs have the behavior
you described. I would have no objection to that, as it is both safe and
consistent.

-kmp