Re: NIL and DEFCONSTANT [Gall: Bug Report]

[Nick Gall <Gall@MIT-MULTICS.ARPA>]

    Date:  2 April 1985 23:14 est
    From:  Scott E. Fahlman <Fahlman at CMU-CS-C>
    Subject:  NIL and DEFCONSTANT [Gall: Bug Report]

    I agree with Moon that it "is an error" to redefine built-in constants.
    It probably is not required that an implementation stop you from doing
    this, but it would be a good idea.

    I think that the description on page 56 is OK as it is.  First it says
    that there are built-in named constants that you don't get to change.
    Here it talks about such things as T and NIL.  Then it says that
    "constant symbols defined by Defconstant" are also treated this way, but
    that they may be redefined if necessary by using Defconstant again.  I
    don't see anything that would imply that T and NIL are implicitly
    defined by Defconstant and that they are therefore redefinable.

    -- Scott


I agree with Moon also.  And I agree that pg.  56 is ok too.  It is pg.
69 that is a little shaky, and pg.  324 DEFINITELY states that NIL and T
are defined with DEFCONSTANT.