CMU Common Lisp supports the IEEE infinity and NaN special values. These non-numeric values will only be generated when trapping is disabled for some floating point exception (see section float-traps), so users of the default configuration need not concern themselves with special values.
[Constant]
Last message occurs repeats timesextensions:
short-float-positive-infinity
extensions:short-float-negative-infinity
extensions:single-float-positive-infinity
extensions:single-float-negative-infinity
extensions:double-float-positive-infinity
extensions:double-float-negative-infinity
extensions:long-float-positive-infinity
extensions:long-float-negative-infinity
The values of these constants are the IEEE positive and negative infinity objects for each float format.
[Function]
extensions: float-infinity-p
x
This function returns true if x is an IEEE float infinity (of either sign.) x must be a float.
[Function]
extensions: float-nan-p
x
extensions:float-trapping-nan-p x
float-nan-p returns true if x is an IEEE NaN (Not A Number) object. float-trapping-nan-p returns true only if x is a trapping NaN. With either function, x must be a float.