I found in the reference manual that eqv? works for NANs. I assume that eqv? or = would both work on infinities. Here again, the science collection uses eqv? for both infinities and NANs - so I may have discussed this with you years ago when I originally wrote them. But I do think that adding explicit nan?, infinite?, and finite? (which is not the same as (not (infinite? x) because of NANs) would be a good idea at some point to reduce the confusion as to what equality operator to use.
On Wed, Oct 27, 2010 at 4:18 PM, Matthew Flatt <mfl...@cs.utah.edu> wrote: > At Wed, 27 Oct 2010 14:20:37 -0600, Doug Williams wrote: > > What is the correct way to test for +nan.0 in Racket? For example, (= > +nan.0 > > +nan.0) = #f. This seems to be the behavior specified in R6RS. In the > > science collection I implemented nan? using eqv?, which seems to work in > > Racket; but the result is explicitly unspecified in R6RS, which I assume > > means that it's up to the implementation. Which pretty much leaves eq? as > > the proper test. R6RS includes primitives like nan? and infinite?, which > I > > included a long time ago in the science collection. Obviously one can use > > them from the r6rs libraries, but should they be moved into the racket > > language? > > `eq?' will not work, while Racket (unlike R6RS) promises that `eqv?' > will work. > > At Wed, 27 Oct 2010 15:15:44 -0700, David Herman wrote: > > Does (not (= x x)) work? > > Yes, that would work too. > >
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