`decode-float', which breaks an IEEE-float into its constituent

sign, exponent and mantissa, is very useful and worth specifying.

See the portable call-with-mantissa&exponent implementation

from SRFI 56.

What's the rationale for the constants instead of the expressions?

If we keep them it's worth noting that e is (flexp 1.0). Also I think

tau is more useful than pi (http://tauday.com/) and worth defining.

Also consider defining the machine epsilon (DBL_EPSILON).

Could you provide an example for:

Flonum operations must be at least as accurate as their generic

counterparts applied to flonum arguments. In some cases,

operations should be more accurate than their naive generic

expansions because they have a smaller total roundoff error.

Alex