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*To*: MOON at MIT-MC*Subject*: wanted: opinions on a benchmark.*From*: George J. Carrette <GJC at MIT-MC>*Date*: Fri, 6 Mar 81 19:52:00 GMT*Cc*: BUG-LISP at MIT-MC, BUG-LISPM at MIT-MC, NIL-I at MIT-MC*Original-date*: 6 March 1981 14:52-EST

Thanks for the explaination. About the divide-by-zero and overflow errors. What I really want is some kind of arithmetic modulo M. However, the description of 24-bit-arithmetic in the Lispm-Manual scared me off a bit. What would be very nice is to be able to use the same generic arithmetic functions, "+","*","//","\", with a "small fixnum" which had certain properties, amoung them "staying small." It is not that I don't like SMALL-FLONUM's, it is just that the algebraic properties of them are not ideal for hidden-line clipping arithemetic. What happens is that because the lisp machine does a lot more CHECKING, this forces the program using them to do checking too, and to compensate for the strange algebraic properties. Its pretty obvious that if one can get the required program behaviour from the properties of the objects being manipulated, rather than from hairy control structure inside the program itself, then it is a win. The Array-accessing problem: Of course, the Maclisp object I used to descibe a CLIPPING-PLANE was a fixed-size hunk, a very simple structure fixed locations of which can be referenced with a single PDP-10 instruction. Lispm-machine arrays have much more complex properties, which simplify the control structure of many of the programs which use them no doubt! -gjc

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