Is there an implementation independent way of representing infinity or not a number (NAN) in Common Lisp? It would need to be a double float, and have both positive and negative values. In SBCL, the results of

(apropos "INFINITY")

include

SB-EXT:DOUBLE-FLOAT-NEGATIVE-INFINITY (bound)

SB-EXT:DOUBLE-FLOAT-POSITIVE-INFINITY (bound)

but I need it to be available in all implementations. I have an addendum to a package to write that runs on all platforms and it needs a representation of infinity and NAN. Even functions from another library would suffice.