[no subject]

[KMP at MIT-MC (Kent M. Pitman)]

    MSG: DIFF   1     
From:     PRATT@MIT-AI
Date: Thu, 24 Nov 78 20:10:25 GMT
Original-Date: 11/24/78 16:10:25 EDT
Subject: Re: What difference does one argument make?
    ...  However, for the case of one argument (- 3) yields -3
    and (-$ 3.0) yields -3.0 as one might expect, whereas (DIFFERENCE 3)
    yields 3.  Does anyone own a program that would not work if DIFFERENCE were
    brought into line?  Does anyone care either way?

(MINUS 3.0) returns -3.0 - the problem is that the two generic operators
map into the single fixnum operator. I would rather see there created fixnum
and flonum analogs of both MINUS and DIFFERENCE rather than have DIFFERENCE
altered. A distinction should be made between the use of the unary minus
and the use of an N-ary minus which just happens to have only one term.
Both can be useful at times. Since there are probably existing programs 
(especially macros) which generate code relying on DIFFERENCE to work a certain
way it seems like these would get messed up by your proposed change. I would
not want to have to search all of my files changing such a thing.

--kmp