This is a dumping ground for random R6RS base library procedures that might be wanted in WG2.
boolean=? compares booleans for identity.
symbol=? compares symbols for identity.
real-valued?, rational-valued?, and integer-valued? test whether a given number object can be coerced to the specified type without loss of numerical accuracy. Specifically, the behavior of these predicates differs from the behavior of real?, rational?, and integer? on complex number objects whose imaginary part is inexact zero.
infinite? returns #t on +inf.0 and -inf.0
assert raises an error if its argument is #f.
There are now tickets to add each of these things to R7RS-small.