max@Neon.Stanford.EDU (Max Hailperin) (03/16/90)
Has anyone explored the possibility of useing IEEE floating-point as a general representation in a manifestly-typed language, with everything other than flonums being NaNs (Not-A-Numbers)? On the surface, this seems both attractive and ridiculous. If I had to make a guess, I'd guess that the former only took precedence over the latter for serious crunching on specialized 64-bit machines. But, the question is, can anyone do better than my 2-minute idle speculation? Thanks.
barmar@think.com (Barry Margolin) (03/16/90)
In article <1990Mar15.211150.19338@Neon.Stanford.EDU> max@Neon.Stanford.EDU (Max Hailperin) writes: >Has anyone explored the possibility of useing IEEE floating-point as a >general representation in a manifestly-typed language, with everything >other than flonums being NaNs (Not-A-Numbers)? The IEEE rule is that any arithmetic involving NaNs must result in a NaN. But if fixnums are implemented as NaNs then this means that (+ 3.0 1) must evaluate to a NaN rather than 4.0, since this would be (+ 3.0 NaN). Perhaps, instead of using NaNs for all non-fixnums you should use NaNs for all non-numbers (NaN *does* stand for Not a Number, so this makes sense). You could then use signalling NaNs, which would cause ordinary IEEE FP hardware to trap on things like (+ 3.0 'a). -- Barry Margolin, Thinking Machines Corp. barmar@think.com {uunet,harvard}!think!barmar