4.6.2 Representability of infinities and NaNs

The specification of the numerical operations is written as though infinities and NaNs are representable, and specifies many operations with respect to these number objects in ways that are consistent with the IEEE 754 standard for binary floating–point arithmetic.

An implementation of Scheme may or may not represent infinities and NaNs; however, an implementation must raise a continuable exception with condition type &no-infinities or &no-nans (respectively; stdlib arithmetic flonums) whenever it is unable to represent an infinity or NaN as specified. In this case, the continuation of the exception handler is the continuation that otherwise would have received the infinity or NaN value. This requirement also applies to conversions between number objects and external representations, including the reading of program source code.